Stewart is hungry. He's munching on potatoes smothered in chicken fat drippings, sitting by a long metal table that once served as a gurney in the morgue at the Treasure Island Naval Base. It's a prominent piece of furniture in what will be the kitchen area for Stewart's new startup. All told, the space is big enough for 75 or so employees, most of whom have yet to be hired. They will theoretically work in this great glass transept at the eastern edge of a massive new building just off of San Francisco's Third Street. He's been here for less than a week.

Stewart (Butterfield) is well known in certain circles as the founder of the ur-photo-sharing service, Flickr. When he and his two partners sold it to Yahoo for, Stewart says, "somewhere between $22 million and $25 million" in 2004, it kicked off the Web 2.0 era and signaled the end of the dotcom bust. Flickr was a treasure chest of innovation, but Stewart never even intended to make the damn thing. He'd set out, instead, to make a game called Game Neverending. It was a financial failure. Flickr was merely based on a set of features broken out of the game, but it took over the company and his life. You may have heard the regrettably trendy term pivot, where a startup abruptly shifts to a new strategy and suddenly thrives. This was one of the original pivots. Everybody does it now.

History has circled back on Stewart. After a few years at Yahoo, he quit and went back to work on his neverending game. This time he called it Glitch, it looked amazing and had a vividly imagined story line, but was conceptually similar to Game Neverending. Years passed. The game failed. Again. Then (again!) he broke out something he and his team had created by accident while making the game. They are now turning it into its own product and hiring a bunch of people to work on it here, just off Third Street.

Slack’s chat function is a trojan horse for bigger ideas. It wants to oversee all your other business software.

On first blush, it sounds boring. Worse, it's a bit hard to explain because you haven't used anything like it before. It's a communications application, based on the system they created while building Glitch. It's called Slack.

To get you in the door, it has a supercharged group chat function, a modern take on the AOL rooms of yore. It runs on your desktop, the web, your phone, and stays in sync as you switch from one to the other. Instead of one big room, it lets you set up channels for various groups and teams, or even for specific functions (like, say, monitoring the @ replies to your company's Twitter feed). And naturally, there's private one-to-one messaging as well.

Yet Slack's well-designed chat function is a trojan horse for bigger ideas. Its ambition is to become the hub at the center of all your other business software. It ties in to many of the applications you use at work: Dropbox, Google Apps, GitHub, Heroku, and Zendesk to name a few. Once they're all connected, it can keep track of most everything you do with them. Most importantly, it's got killer search built right in. "Right now, your data ends up a little bit in Twitter, a little bit in Zendesk, a little bit in GitHub," Stewart says. "Slack is the one mutual platform where all those things come together. That's the longer-term thinking."

The morgue table at Slack HQ. Ariel Zambelich/WIRED

The payoff is that it makes collaborating way easier than whatever you're doing now. Let's say you drop a link to a PDF stored in your folder in your company's Dropbox. People on your team will see this file pop up in Slack, with a summary, and can click on it to read—right there in the app. Your colleagues can review it, make notes about it, and comment on what you ought to do next without ever leaving the application. One of your team members says, "You really did it, bro! This is a massive thought bomb." Yay! They adore you.

Not only did Slack make sure the document went to all the right people, but it also indexed the full text of the document, as well as the conversation that took place around it, and attached the conversation to the document in its database. Now: Imagine that weeks pass by. You, sadly, die unexpectedly. Now that you're gone, your coworkers need to pull up the document, but they have trouble finding it in your disorganized Dropbox folder. So instead they search Slack for "massive thought bomb" and, presto, there it is, along with all your notes and the feedback you received from your team. That's Slack.

It's already a press darling, embraced by all the trendy and brave young media properties—Vox Media, Buzzfeed, Medium and Gawker Media are all paying customers. But so too are Expedia, Intuit, Dow Jones, eBay, Paypal, Mint, Citrix, Heroku, Happy Cog, Wall Street Journal, Motley Fool, The Times of London, Crossfit, MyFitnessPal, DailyBurn, Fitocracy, Rdio, Pandora, Nordstroms, Polyvore, Vinted, Urban Outfitters, Blue Bottle Coffee, GoDaddy, Urban Airship, Sony, Dell, AOL, ITV, NBCUniversal, Lonely Planet, TV4, Galen Healthcare, Shutterstock, SmugMug, Stripe, Venmo, Braintree, Airbnb, Adobe, Typekit, Behance, Foursquare, Yelp, WordPress, Moz, SurveyMonkey, Tumblr, Trunk Club, Seagate, Tibco, Trello, and HBO. Phew!

Slack is so beloved that some companies have begun mentioning it as an employment perk alongside on-site massages and bottomless bacon-tray Fridays in their job listings. Like: We have a dry cleaning service, an ice cream parlor, and… Slack.

Since its public debut in February, Slack has been growing at a rate of 5 to 10 percent a week and now has more than 120,000 daily users. Fully 38,000 people from 2000 different organizations pay for the full-featured version of the service. It has so far pocketed $1.5 million in revenue. If just those subscribers keep paying, Slack would pull in $3.5 million a year. But it is adding so many subscribers so fast, that the annual billing projections are growing by $1 million every six weeks. And people do tend to stick around at an astonishing rate: 93 percent of people who try Slack keep using it. So it's no wonder that the company has raised some $60 million in venture capital—$43 million in April alone.

A plastic version of the Slack logo on the windowsill, waiting to be mounted on the wall. Ariel Zambelich/WIRED

But these are sweatsock numbers. The kind of thing you toss in the hamper in an offhand fashion, but that only hints at your larger ambition and work. Slack wants to get huge. It wants to get to a place where it is the one application that everyone in your company runs all the time, no matter what else they are doing. It wants to end interoffice email. It wants to be the next Microsoft—not the current, cowed, pathetic company looking for a comeback. No, it doesn't want to be Expendables Stallone-era Microsoft, it wants to be Rocky/Rambo Stallone-era Microsoft.

But—and this is a key but—Stewart wants Slack to be the Microsoft you want to use. The software itself is easy to understand. It does the things you expect it to do, as you expect it to do them, and holds your hand when it introduces new concepts. You can change the way it looks in subtle ways to make it your own, but even on a fresh install it's just pretty to look at. Every time you fire it up, it greets you with whimsically twee inspirational messages. It says "Each day will be better than the last. Especially this one." Or: "Please enjoy Slack responsibly." Or Stewart's favorite: "What good shall I do this day?"

Slack's strategy is to insinuate itself into the workplace from the bottom up. The idea is that it will get so popular inside organizations that IT departments will have to embrace it. When you've got just a few people using the free version, it works well enough. But as it catches on in the workplace, features like unlimited message search and custom integrations with other software become increasingly vital. And to get those features you have to pay to upgrade. By now, you're hooked. So you convince your CIO to pony up—or at least, that's the hope. I mean, it's working for Dropbox, right? Until now, Slack hasn't even done any advertising. It has grown entirely (and phenomenally) by word of mouth.

He may have stumbled into Slack on the way to another adventure, but it has turned out to be one hell of a ride.

There are still a lot of challenges, especially if it wants to make its way from startups and tech firms into the suites of the Fortune 500. At $7 per user per month, the paid version of Slack is expensive. Another issue for large organizations is that Slack's software runs remotely on some far-flung Amazon server. Giant businesses, or ones with inscrutable security requirements, often want something that can run locally, on their own servers and machines. Also, Slack is designed to help businesses expose all their internal communications—but while that's a popular concept in Silicon Valley it's something many traditional businesses may be adamantly opposed to. And then there's email. Slack doesn't support email! For an all-in-one corporate communications system, this is an omission as large as a tech bro's ego. (Email integration is in the works, Stewart says.) And maybe the biggest challenge of all—if they want to get not just big but huge—will be explaining what the hell Slack is and who might want it in a way that mom and pop small businesses across this great nation can easily understand.

But, for now things are looking hot. Stewart knows chances like this are rare. If he can pull it off, Slack could be worth billions—which would translate into a huge payday for his investors, his employees, and (yes, yes) himself. He may have stumbled into Slack on the way to another adventure, but it has turned out to be one hell of a ride on its own. Making good software that people love is fun. And hey, he wouldn't mind having a billion dollars. So now, clients are rolling in with cash. Investors—five to 10 a week—are calling Stewart to get in on the action. Interested parties have made interested inquiries as to whether or not he's ready to sell the business outright. There's money in the air. You can smell it. Or, maybe, that's just chicken fat.

Stewart and his mother behind the log cabin he grew up in; undated photograph. Courtesy of Stewart Butterfield

The Dharma Days

Like a lot of 19-year-old kids in 1968, David Butterfield was disillusioned with American society. The Summer of Love had given way to the Spring of Assassinations as first MLK and then RFK were felled by bullets. David dropped out of Harvard, moved to France, and promptly got a telegram from the United States Army. Forty-six years later, he still recalls its opening line from memory: "Greetings, you are now a member of the world's finest fighting team." Hup. Even in the Army he was outspoken about his antiwar views.

So to reward him, instead of making him a medic, as he'd hoped, the Army made him a sergeant and put him in charge of a mortar platoon from North Carolina. Most of these guys were poor, black, and uneducated, and all of them had been given the choice of joining the Army or going to prison. Now, it was off to Vietnam to kill or be killed despite the fact that they, much like Muhammed Ali, got no quarrel with them Viet Cong. This presented a moral crisis for David, which he solved one night by driving to Canada instead of back to base. As soon as the car chugged across the border, he jumped out and yelled and screamed into the night sky; a deserter.

In Quebec, David linked up with the American Deserters Committee (you can look him up in FBI File number 105-185434). More important, he fell in love with a woman named Norma, and together they went west to Vancouver, and then north on Highway 101 until it ran out and they couldn't go any farther up the road.

There, in Lund, British Columbia, formerly a sleepy fishing village peopled by the descendants of Swedish settlers and Salish natives, some 500 or so hippies were getting back to the land (including not one but two psychiatrists). They spent the winter in a squatter's cabin on a nearby island. In the spring, David built a home from the ruins of a homesteader's 19th-century log cabin. There was no running water. No electricity. No phone. In 1973 Norma gave birth to their son, Dharma Jeremy Butterfield. (The psychiatrists delivered the baby.)

Dharma (pre-Stewart, center) at his 5th birthday party. Courtesy of Stewart Butterfield

But time passes, and people make compromises. "We had a lot of ideas when we were young about building this whole new society—which in a way we did," David says, calling from aboard a ferry in British Columbia. "But the truth of it was that that society wasn't any better than the society we left."

In 1977 the family moved from Lund to Victoria—mostly for the benefit of their son. They'd already been building and renovating property, and now they made a career out of it. They were successful. David grew a mustache and bought a sailboat, which made for a great tax shelter. The nice thing about rejoining capitalist society is that you can buy your kid a computer when he's just seven years old. And the nice thing about getting older, at least for Dharma, is that he could legally change his name to Stewart, which he did when he was 12 years old. It was the most normal, un-Dharma-like name he could think of. Today, he wishes he'd picked a different one. "There are no good characters named Stewart," Stewart says.

Stewart was the kind of kid who went to China (at 16, by himself, in the '80s). At Canada's University of Victoria he majored in philosophy—he loved Spinoza—and got his degree in it. At Cambridge he scored a master's degree in the philosophy of the mind and was preparing to go for a PhD when, oh my God, have you even seen the internet? The internet! He was also really into jam bands. Rec.music.phish got him online, but the web kept him there.

His first real job was working for a dotcom whose entire business model was based on a fundamental misunderstanding of how people would come to use the internet, plus domain squatting. Look, it was the '90s, OK? In 2000 on a trip to San Francisco, he met a blogger named Caterina Fake and eventually talked her into coming to visit him in British Columbia. They fell in love, and got married in 2002.

Just after their honeymoon, Stewart, Caterina, and a programmer named Jason Classon formed a new company called Ludicorp. The idea of Ludicorp was to make a new kind of game, something you could play forever without winning or losing. It was called Game Neverending. It was different. Weird, even.

"Stewart was always coming up with great puzzles and games," recalls Paul Lloyd, a friend from college, who worked with him at Ludicorp, Flickr, Glitch, and now Slack.

Stewart Butterfield as a child; undated photograph. Courtesy of Stewart Butterfield

An English blogger and programmer named Cal Henderson ran a fan site for the game, and eventually broke into one of the company's internal mailing lists, where he announced himself a few weeks later. Stewart hired him.

Despite having interested, even ravenous, fans like Cal, the business wasn't working. Everyone at Ludicorp got together to vote on whether they should throw more resources at it or devote themselves to this other thing, this image-sharing thing, a feature of the game that they thought might have potential to keep the main business afloat. Cal and another Ludicorp engineer named Eric Costello were tapped to lead its development. (The pair along with yet another Flickr alum, Serguei Mourachov, went on to cofound Slack with Stewart.) "He promised me I could work on the game again if I worked on Flickr," Cal explains. "It only took five years."

In April 2004 Stewart was scheduled to give a talk at an O'Reilly conference called Etech in San Diego on some pretty technical things found in Game Neverending—APIs, REST, RSS. It so happened that these were all features of Flickr. He decided to use it as a venue to announce and launch his new thing instead. Surprise! Flickr wasn't even finished.

The demo blew everyone’s mind. By the time they walked out of the room at ETech, Flickr was famous.

The team pulled an all-nighter to get the presentation ready. At around five in the morning, Cal added the last touch: a way to upload images via email, so you could share pix from a mobile phone. The demo blew everyone's mind. By the time they walked out of the room at ETech, Flickr was famous.

In 2004, photo sharing in the cloud was wild stuff. But Flickr was also groundbreaking in a number of other ways. The service pioneered a cocktail of features that we would come to associate with the Web 2.0 era—the transition period when the world moved from largely static web pages to ones that act more like interactive applications. Although Delicio.us was the first major service to introduce what came to be known as tagging, Flickr took it mainstream. Every time you tag someone in Facebook or add a hashtag on Twitter, you can thank Flickr.

It also figured out the concept of "authing in." You know how you can use Facebook or Google or Twitter to log in to a site, just by clicking a button, without actually having to surrender your username and password? Yeah, Flickr did it first. It was even at the forefront of social networking: A decade ago, it was letting people add friends and contacts with varying levels of permission. You could identify someone as a contact, a friend, family or all of the above, and vary what they saw based on the relationship. Flickr also introduced the world to activity streams—the running tallies of what a user does on a site.

But its power move was something called an open API. To see just how far we've come, nobody who is anybody even uses the term "open API" anymore. It's just API, now. But prior to Flickr, websites' application programming interfaces—or the set of rules that govern how a program can interact with something in a database—were typically reserved as internal tools. Flickr threw open the doors and let anyone on the Internet prong into its API, the first big service for consumers to do so. It was a philosophical statement: Our data is better when we let other people do things with it. This is accepted gospel now, but at the time it was a new and radical notion.

The original Ludicorp team (plus a few friends), dressed as Cal to celebrate his birthday—affectionately known as "Calmas." Courtesy of John Allspaw

It was precisely the kind of thing a philosophy major who spent his childhood on a commune without running water or electricity might come up with. "I related to the whole hippie, acid-test confluence of the early internet," Stewart says, looking up at the vast empty space overhead in the Slack office. "The idea that we should be open and interoperate with our data resonated with me." He pauses. His tone shifts. "It was also something people could get behind, and make them want to support us. You know? We didn't think about Dvorak or Mossberg. We thought about Cory Doctorow." That is, they didn't care about the mainline tech press, the people writing about IBM and Apple and Adobe. They wanted the information-should-be-free set. The zealots, who would spread the gospel out on the open web.

A year later, Stewart and his two cofounders sold out to Yahoo. Innovation at Flickr turned blue and choked out.

It worked. Flickr got huge with bloggers, who finally had a tool that made photo management and publishing super easy. (Back then, Blogger didn't let you upload pictures.) At about the same time, everyone's phone suddenly had a digital camera, and we were all taking pictures. We desperately needed an easy way to share them. And, hi, hello, Flickr. You're pretty.

A year later, Stewart and his two cofounders sold it to Yahoo, and relocated from Vancouver to the Bay Area. Yahoo was (and is) its own terrible joke. Innovation at Flickr turned blue and choked out. You could write a whole other story about what Yahoo did to the once-young, vital company it bought. They sold out to Yahoo assuming that they'd be backstroking in rivers of money and terabytes of memory. Instead they had to fight for everything: servers, people, time.

Stewart tried to quit after three years. But Caterina had just left too, and lots of other high-ranking people were fleeing Yahoo, and so the company talked him into staying a few more months to help avoid the appearance of a mass exodus. ("I was told it would look bad if I left," he says.) During his last several months at Yahoo, he didn't actually do anything. He didn't even have to go into the office, like that guy on Mike Judge's HBO show Silicon Valley, has to do. With his time finally served, he told his manager, Brad Garlinghouse, that he was leaving. Garlinghouse asked Stewart to write a resignation email that could be forwarded to Yahoo's human relations department. So Stewart did.

From: Stew­art But­ter­field Sent: Fri­day, June 13, 2008 10:57 AM To: Brad Gar­ling­house Sub­ject: Resignation Dear Brad, As you know, tin is in my blood. For generations my family has worked with this most useful of metals. When I joined Yahoo! back in '21, it was a sheet-tin concern of great momentum, growth and innovation. I knew it was the place for me. Over the decades as the company grew and expanded, first into dies and punches, into copper, corrugated steel, synthesized rubber, piping, milling equipment, engines, instruments, weaponry and so on, I still felt at home because tin was the core of the business… Since the late 80s, as the general manufacturing, oil exploration and refining, logistics and hotel and casino divisions rose to prominence, I have felt somewhat sidelined. By the time of the internet revolution and our expansion into Web Sites, I have been cast adrift. I tried to roll with the times, but nary a sheet of tin has rolled of our own production lines in over 30 years. In my 87 years service, I've accomplished many feats, shared in the ups and downs, made great friends and learned a tremendous amount … but there is a new generation now and it would be unfair not to give them a chance. Those that started in the make-work programs of the depression, on the GI programs in the late '40s and even those young baby boomers need their own try without us old 'uns standing in the way. So please accept my resignation, effective July 12. And I don't need no fancy parties or gold watches (I still have the one from '61 and '76). I will be spending more time with my family, tending to my small but growing alpaca herd and of course getting back to working with tin, my first love. Your old tin-smithing friend and colleague, Stewart Butterfield

It was likely the most widely read memo ever written by a senior director of product management at Yahoo. It was forwarded and re-forwarded and fwd: fwd: re: forwarded some more. It wound up in all sorts of blogs, on Valleywag, and even in The Guardian. Stewart says he's still surprised with how widely it was circulated. It was also the endpoint of a very tumultuous year. He had a new daughter in July 2007, and six months later, he was divorced. In another six months after that, he was finished with Yahoo and Flickr too.

"I felt like my whole life was falling apart and that I should leave and go to India or something," he says, sighing. "It was a horrible period." Instead, he went back to British Columbia, where he founded a new company to start building Glitch. He still lives there today, in the Yaletown neighborhood of Vancouver with his girlfriend of five years. He spends every other week in San Francisco.

Selling Out, Cashing In

There's a spreadsheet, a list, sortable in the way everything is now, and it names Slack's clients in row after row and column after column that can be sorted in all sorts of interesting ways, because data has now replaced God in the Far American West. We worship it and fear its revelations. All that matters is how much something is: how much it's used, how much it's viewed, how much it costs, how much it pays, how much it grows, how much it shrinks, how much it is returned to again, how much it is abandoned.

Stewart is looking at his spreadsheet of clients. He knows things are good, but here he can actually see who pays and who doesn't. Remember, Slack charges $7 per person per month to use its paid version. He sorts the list by the number of users each team has. Far up near the top is Gawker Media. Gawker is still freeloading. Just days before, its new editorial director Joel Johnson lamented on Twitter that Gawker was shutting down its group chat system, Campfire, after using it for 10 years. The reason was banal: 37 Signals, the company that made Campfire announced it would no longer be supporting it. That meant Gawker Media had to find something new.

Campfire is a Gawker tradition, and arguably one of the things that helped it grow into a colossus of snarky megablogs. It lets its editors quickly marshal far-flung writers and throw them at stories. It served as a place to strategize, to coordinate coverage, to blow off steam. Now, Joel had to replace it. Joel, being Joel (someone who thrives on bomb-throwing and button-pushing and competition but who is also both a genius and a genuinely lovely person), tweeted that he was replacing Campfire with Slack "which we've figured out how to use without paying for." This nails one of Slack's biggest business problem in a single tweet. Stewart saw the message and simply replied, "Staring contest."

A week later, there was Gawker, high up on Stewart's spreadsheet, still sponging. Gawker has nearly 300 people using Slack and none of them paying. Stewart is quietly confident. He smirks. "They'll blink," he says, and grabs his jacket to go get coffee. Stewart is thirsty.

Everyone at hot startups drinks a lot of coffee. But you can't drink just any coffee. Nobody can drink just any coffee anymore and be taken seriously. (Except for those who proudly and intentionally do so. The key is doing it with intention. But you can't just saunter up to Starbucks or Dunkin' Donuts and get a coffee and actually think it's good.)

And so five times in a row, Stewart stalks past the Starbucks at the corner of Second Street and Folsom. He's looking for an independent cafe that is supposed to be… right around here… somewhere…

Stewart can be compulsive. That same day, on the same block, a woman in her late 40s or maybe early 50s, clearly not part of the trendy tech set, stops him and asks if he can tell her how to get to the ballpark. Yes! Of course! Just follow Second Street all the way to its end and take a right. It's probably a 10-minute walk. But then she asks if he's heard of Dropbox (um, yes) and how far the Dropbox office is from the ballpark. She's actually on her way to a job interview. Stewart immediately wants her to get the job. He asks what time she is meant to be there. He grabs his phone from his pocket, looks up the address, and gets walking directions. Turns out it is more like a 19-minute walk.

He becomes visibly concerned. She needs this job! He suggests she take a bus, and looks that route up for her, too. It turns out the 10 isn't running from its regular stop (road construction), so he looks around and helps her find the temporary stop. She asks if he can change a twenty. He looks in his wallet, there are a few singles, and some tens and twenties, but he can't make change. The bus is coming. It's all happening too fast. He looks indecisive for a second, staring down at the cash. Two bucks—exact fare—stare back at him. He hands it to her, he hugs her, and he wishes her luck. She makes the bus.

But back to coffee. Stewart is spending a lot of time getting coffee and sandwiches and beers with the media these days. These are morsels of obligation. The press loves him because he's both successful and incredibly frank. Ask him a question and he tends to speak in answers, rather than statements. He curses freely. It's a little bit shocking. He shrugs it off. "It's easy to be forthcoming when everything is good," he says. (Someone should tell Tim Cook.)

If you want good people, your conference room had better be a log cabin. Or the war room from Dr. Strangelove.

A lot of reporters want to talk to him right now—very many! There's nothing like $43 million in fresh funding and a hotshit product from a ginger-headed, e-cig smoking, two-time visionary to make the media sit up and notice. The Wall Street Journal, The Atlantic, WIRED, Valleywag, Pando Daily, and a host of others are either courting him or have already made out, eager to attach his story and his image to their own. "I heard from the Slack people that you're writing a Slack feature," The Atlantic's Alexis Madrigal says in a wee little instant message window. "They were like sorry you can't meet with Stewart. Honan is writing a thing."

And it isn't just the American media. A few weeks ago Stewart gave an extensive interview to a Chinese website. (Really, it's like the Chinese TechCrunch, he explains.) The media seems to like him, and he mostly likes the media.

Mostly. "I fucking hate Valleywag," he says, finishing his macchiato. As he puts his cup down, he reels that back in a bit, recalling a pleasant interview with one of its writers. "Or at least I hate Sam Biddle." Sam Biddle, for those of you who have yet to be personally insulted by him, is Gawker's Valleywag editor, tasked with covering the technology industry and its foibles.

Valleywag gleefully channels the hostility and contempt people have toward tech-types in San Francisco and New York right now. We have to stop Google! Have you seen what Facebook is doing now? Tech bros are the new investment bankers: greedy, clueless, chauvinistic, unforgivably rich. Valleywag delights in popping the industry's self-inflated balloons.

The problem, Stewart says, is that Sam can be disingenuous in a manner that borders on lying. He cites a Valleywag story about Ben Horowitz—an old friend of Butterfield's whose firm is an investor in Slack. In the story, titled "Prominent Venture Capitalist Discovers Black People," Sam cast Horowitz, who is married to a black woman, in a light that made him look racially insensitive. Stewart insists that Horowitz's words carried the exact opposite intent, and Sam had to know it. (Sam points out that the post in question was based on a quote from Horowitz that initially appeared in The New Yorker, which it changed after publication. "I absolutely did not deliberately misinterpret or misconstrue Ben Horowitz' words," Sam says via instant message.)

Stewart doesn't think Silicon Valley is beyond skewering, and God knows he's class-conscious. He lists the ways that he's privileged: first and foremost he is a man, and a white man at that, which he notes gives him a huge advantage over being born black or a woman, and what's more, he was born to affluent parents in an English-speaking country, at just the right moment in history for what he does. Oh, and he grew up on a commune.

His phone rattles with a message. It's Joel Johnson. He's blinking. All of Gawker is going to begin using the paid version of Slack. "We decided to pay so we could have maximum integrations," Joel says, like all good tech journos, via instant messenger. "And because I like paying for software that we use. The price is so fucking painful, though. It's just not priced for large organizations."

But nonetheless Gawker slid its dollars across the table, and now everyone at Gawker Media uses Slack. Even Valleywag.

Ariel Zambelich/WIRED

Ice, Ice, Baby

The thing about working at a hot, well-funded startup these days is that it's still really hard to staff up. Equity, salary, extravagant benefits packages, and quirky perks (Slack socks!) are simply table stakes.

If you want to attract good people, if you want to impress that highly talented engineer when she walks through the door and strolls into your conference room after visiting the facilities at Dropbox or Airbnb or Uber or any number of other San Francisco-based businesses, your conference room had better be a log cabin. Or at the very least you're going to need it to be a fully realized re-creation of the war room in Dr. Strangelove. What? You don't have a war room? Everyone has a war room. Anyway, your space had better be nice, otherwise why not just work at Google? Stewart is aware of this, and so he and Cal are spending the day looking at office furniture porn and talking about interior designers.

"Look at this," Stewart says, pointing to his screen at a long wooden table with recessed bins for power and ethernet, surrounded by a selection of thousand-dollar chairs. "That's $100,000. Do you think that's worth $100,000? It looks like shit." They are an odd pair, Cal and Stew, when you see them together. Stewart tends toward designer shirts and respectable slacks on top of wing tips, all whites and pastel colors. Cal is a parody of an engineer. He shows up to work in flip-flops and cargo shorts, even on coldish summer days in San Francisco. He's mostly quiet, but when he speaks it's in a loud voice, whereas Stewart is very talkative but almost whispers at you.

At work, Cal HAMMERS on his keyboard, and HAMMERS and HAMMERS, and occasionally the room lights up in laughter in response to his HAMMERING (or sometimes it's in response to the miniature drone he flies through the air). Everyone at Slack communicates, naturally, via Slack. When night comes, Cal and Stewart head to dinner at Bar Agricole, a popular spot for the city's power-boozing tech elites. The people you'll bump into there—Ryan Block at a table with Veronica Belmont, Om Malik downstairs in the private room with Nick Bilton and Matt Buchanan and Nicole Perlroth—are the who's who of right now, unwinding in a casual no-pressure setting.

And no wonder. I mean, the food is amazing. Have you even tried the Farinata with purple artichokes, chrysanthemum, and parmesan? Oh, you have to try it. But really it's about the drinks, the cocktails, man, oh, wow. The ice! Hold your glass up to the light, maybe it's a Whist Cocktail or a House Old Fashioned, and look into it and you won't see the cube, although it takes up almost the entire glass by volume. It's a great gaping gaw of unglistening luxury. Artisanal ice. Stewart and Cal are keen to talk ice. Cal has already backed three different bespoke ice makers on Kickstarter and knows his ice.

And why shouldn’t they have a cold drink? They are on top of the world, having built a truly sublime piece of software. Make ice at high enough pressure and you get something perfectly transparent, just like what you see in this glass. (Or more accurately: just like you don't see in this glass.) It's very important that you don't see it, because the cloudiness in ice—the white of ice—is caused by air. Air pockets increase the surface area of ice, so more of it comes in contact with liquid and thus waters down your very expensive cocktail. Which is bad, according to Cal. Cold is good. Watery is bad. Both are impressed with the ice here at Agricole. It's very good ice.

Stewart and Cal at the Slack offices. Ariel Zambelich/WIRED

Consider the lowly link. Drop a link to a Washington Post story in an app like HipChat and you'll see a URL. Drop the link in Slack and what people see is the link, with the name of the publication right under it, followed by the headline, a byline, and a brief summary of the story below that, and a related image. Instead of an unparsable string of characters that may or may not lead to Goatse, you get a working summary of what you're about to see.

This appears like magic, instantly. But it belies some very sophisticated, very fast things happening behind the scenes. It's a powerful experience that looks simple, but it speaks to how sleek Slack's underlying code is. You don't really see it. It's very good ice.

"We like making really good software," Stewart says, explaining why he can be in a software business that specializes in something as boring as business software. "It's pleasurable," Cal says, completing the thought.

WIRED: What's your ambition?

Stewart: (straight faced): Be the next Microsoft.

Cal: (wrinkling nose): Doesn't that make you quite sick?

Stewart: Well, a little.

Cal: We could be the next Microsoft if I can be Paul Allen.

(Both take a drink. Stewart picks up the check.)

Of course, the only reason they get to make this really good software that everyone wants to use is because they keep failing at making a game that lots of people want to play. You could advance a theory as to why that might be. Maybe the people this game is designed for—tech savvy, forward-thinking types who care deeply about things like interactive design—don't want to just play for the sake of playing. Maybe those people want to play to win.

The front entrance to the new Slack office. Ariel Zambelich/WIRED

Goodbye to You, Glitch

In October 2012 Stewart walked across Vauxhall Bridge over the Thames in London with an old high school friend, Alexander Gilly. They had been pals since they were teenagers, and a few years earlier, when Stewart was about to embark on Glitch, he called Alexander to come visit in Canada, to brainstorm how the game might work. (What if it all took place in the imagination of 11 giants? Ohhhhhhhh! That's a great idea!) Now, here in London, he told his longtime friend that he had decided Glitch had to end.

"He said he was very sad about it but felt it was the right thing to do," Alexander says, "because it had become apparent that they weren't getting the numbers necessary to make it viable." It was painful.

Later that month, he told his investors and cofounders, and then 48 hours later broke the news to the rest of the team. He gathered his crew in Vancouver and placed a conference call to the handful of employees in San Francisco. He was crying on the phone. They uploaded an archive of all the art, music, player profiles and even the code from the game to a web site—it's still there—and contributed the art and much of the code to the public domain. He helped all his employees find new jobs. And he managed to not burn through the entirety of the money investors had given him.

Now that Glitch has morphed into an actual success, now that Slack is popular with all the cool kids, he's faced with an opportunity and a challenge to pay back the people who stuck with him—like the employees from Glitch who chose to exercise their options (basically buying into the company when it wasn't clear it had a future) and now stand to be repaid many times over.

How much they end up with depends on what Stewart decides to do next. "The biggest thing I worry about with Stewart is that he'll get a compelling offer too early," says Josh Pritchard, who runs Slack's analytics. Josh was an early Facebook employee who (let's be real) is already rich. He thinks Slack is on a similar trajectory, that Stewart is even more of a visionary than Zuckerberg, and that there's going to be a lot of pressure to sell.

Stewart readily admits he sold Flickr too early. "If we had waited six months we would have made much more money. If we had waited a year we would have made 10 times more money," he says. He regrets it now. But at the time, after the dotcom crash, the Nasdaq plummet, and September 11, deals just weren't happening. All his advisers and investors told him to go for it. It was hard to know what to do.

In the wake of WhatsApp (a $19 billion sale to Facebook) and Beats ($3 billion to Apple) and even Instagram (a lousy $1 billion, Facebook again), $22 million now seems like the kind of money you dig out of your wallet to give a stranger at the bus stop. But for the team at Flickr, it was life-changing. Slack, on the other hand, is looking at something more like first class airfare.

Such temptations aren't easy to resist. "We could sell it right now for a billion dollars," Stewart says, and then shakes his head like he's trying to wake up from a weird dream. "Which sounds fucking mental. But the thing is, those options aren't going to go away."

He admits that if the right offer comes along, the kind of offer that only three or four companies in the world could come up with, he would have to jump. But what is that? Five billion? Seven? Ten? It's hard to know, because in Silicon Valley today, money has lost all meaning and value. It is an abstract construct that can be exchanged for homes and Teslas and handmade selvedge denim jeans flown in from Japan, but nobody really has any idea what constitutes "a lot" anymore.

At some point however, he would be obligated to all those who've stuck with him and to all those who have given him money. Yet his ambition is to keep growing and building Slack on his own terms.

"I want to keep going," he says. "And I think everyone else does too." He's hungry. He wants to win.

He doesn't finish the potatoes.

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