Home does put people—your people—front and center. And Zuckerberg is probably hoping that most users choose it over the standard Facebook app. The catch is that not everyone can participate, even if they want to. At launch, Home is limited to a few Android phones; iPhone users are shut out. Apple enforces its own look and feel, and allowing a developer to take over the lockdown screen is currently unimaginable.

But there are plenty of things that were once unimaginable that have come to pass. One of them is the personal evolution of Facebook’s CEO. Accounts of Zuckerberg’s early years as a founder paint him as callow. But in recent appearances—and interviews like this one—he has been articulate, engaging, and at ease. Clearly Zuckerberg is at home at Facebook. Now his task is to make us all feel that way.

What led to your building Facebook Home? Facebook occupies an interesting space in mobile. We’re not an operating system, but we’re not just an app either. Facebook accounts for 23 percent of the time people spend on smartphones. The next-biggest ones are Instagram and Google Maps, which are each at 3 percent. For the past 18 months, we spent our efforts building good versions of Facebook’s mobile apps. But the design was still very close to what we have on the desktop. We knew that we could do better.

Why not just build a phone? I’ve always been very clear that I don’t think that’s the right strategy. We’re a community of a billion-plus people, and the best-selling phones—apart from the iPhone—can sell 10, 20 million. If we did build a phone, we’d only reach 1 or 2 percent of our users. That doesn’t do anything awesome for us. We wanted to turn as many phones as possible into “Facebook phones.” That’s what Facebook Home is.

It’s only available on Android phones. Isn’t it ironic that your mobile strategy is now tied to Google’s operating system? We have a pretty good partnership with Apple, but they want to own the whole experience themselves. There aren’t a lot of bridges between us and Google, but we are aligned with their open philosophy.

So do you think in, say, two years you will have this on the iPhone? That’s above my pay grade to be able to answer that.

That’s a pretty high pay grade. Look, I would love for that answer to be yes. Facebook is in a very different place than Apple, Google, Amazon, Samsung, and Microsoft. We are trying to build a community. We have a billion folks using our services now, and we want to get to 3 or 5 billion one day. We’re going to do that by building the best experience across all devices. Android is growing quickly, and we’re excited that the platform is open and that it allows us to build these great experiences. I think that this is really good for Google too. Something like this could encourage a lot of people to get Android phones, because I think people really care about Facebook. In a lot of ways, this is one of the best Facebook experiences that you can get. Of course, a lot of people also love iPhones—I love mine, and I would like to be able to deliver Facebook Home there as well.

Facebook now calls itself a “mobile first, mobile best” company. If you had started the company in 2013, would you have done it as a mobile app? I don’t know. Maybe once or twice a year I’ll just take a few days off and wander around and ask myself, if I were starting from scratch today, and I weren’t running Facebook, what would I build? I look at this mobile trend in light of the law of sharing, our equivalent of Moore’s law, which states that the average amount of information that a person shares doubles every year or so. Figuring out what the next big trend is tells us what we should focus on.

OK, so what is the next big trend? The big stuff that we’re seeing now is sharing with smaller groups.

How would you implement that? Do you do it within Facebook or with separate apps? There’s a place for both. There’s a place for a service that only communicates with your core friends and family, and I think that’s going to be ubiquitous. But there are other great services out there doing great things. Instagram is a good example of this. They just crossed 100 million active users. It’s a much smaller product by Facebook standards, but it’s a really meaningful product.