Amazon CEO Jeff Bezos during the 32nd Space Symposium in Colorado Springs, Colorado, on April 12, 2016.

Amazon.com founder Jeff Bezos may have surpassed Microsoft co-founder Bill Gates to be the richest person in the world, but there's one title he isn't likely to claim: world's most generous.Even with more than $90 billion to his name, Bezos has yet to make a major philanthropic mark, but with the new mantle of the world's richest, the pressure on Bezos to give will only grow. Nonprofits and other foundations are desperate to see what he'll do, says giving consultant and researcher Amy Schiller. "Bezos has probably had philanthropy in his mental cart for a while," she says, "and kept clicking 'save for later.'"As Gates built Microsoft, he also faced increasing pressure from the public -- and even his own parents -- to give more. When his mother prodded him one night, Gates snapped back, "I'm just trying to run my company!" the Wall Street Journal reported in 2009. Gates didn't fully throw himself into philanthropy until he stepped down as chief executive officer of Microsoft in 2000, but since then he's helped build the Bill & Melinda Gates Foundation into the largest foundation in the country. A representative said Gates was unavailable to comment."Jeff is probably not quite ready to step down yet, but this is a guy who, like Bill, is fixated on changing the world in really important ways," says Ed Lazowska, Bill & Melinda Gates Chair in Computer Science & Engineering at the University of Washington, who has solicited donations from Bezos. "It's a full-time job. You have to imagine he will be every bit as philanthropic as Gates. Nobody has any right to make demands, and they have to give the guy time." Amazon declined to comment.Some tech founders have made large charitable commitments while still running large businesses. Facebook CEO Mark Zuckerberg and his wife, Priscilla Chan; Netflix CEO Reed Hastings and his wife, Patty Quillin; and Salesforce.com CEO Marc Benioff and his wife, Lynne, have all signed on to the Giving Pledge, vowing to give away the majority of their wealth. The group was started by Gates and Berkshire Hathaway CEO Warren Buffett.Making a major commitment takes humility and years of research to go down the right path, so for someone as work-obsessed as Bezos, "you'd really want to have a trusted partner or set of partners around you," says Jeff Raikes, a former Microsoft executive who ran the Gates Foundation for almost six years. He says Melinda Gates and ex-Microsoft executive Patty Stonesifer ran the Gates Foundation while Bill was still devoted to Microsoft, and Raikes says his wife, Tricia, took the lead when he was still working full-time and they decided to put $100 million into their own foundation, which they now run together.Much of the known personal giving associated with Bezos so far has been driven by his parents, Mike and Jackie Bezos. He sits on the board of the childhood-education focused Bezos Family Foundation, which his parents run. As of 2015, his parents had donated more than $68 million of Amazon stock to the foundation, tax filings show. Bezos had given about $6 million in stock to the foundation. Separately, the Bezos family has given $65 million over a decade to Seattle's Fred Hutchinson Cancer Research Center, which does cutting-edge work on cancer cures. "My parents rock," Bezos tweeted when the latest gift was announced.If Bezos makes a major personal philanthropic push, it's unclear what causes would capture his interest. "His giving so far is not meaningful in terms of a direction," says R. Joe Ottinger, CEO of iInnovate Leadership Network in Seattle, who has written about giving from tech executives. Bezos' personal donations have included $1 million to Code.org, which aims to have all schools teach computer science; support of Worldreader, a nonprofit founded by a former Amazon executive to use e-readers to promote literacy in the developing word; and $10 million to Seattle's Museum of History & Industry. Bezos and his wife, MacKenzie, donated $15 million to their alma mater, Princeton University, for neuroscience research, and they also gave $2.5 million to a political action committee in support of legalizing gay marriage in Washington in 2012.As for Amazon, after years of being largely MIA as a corporate donor in Seattle, the company has stepped up its giving, mostly around the growing inequality in the city, which some activists and politicians have partly blamed on Amazon. Last year the retailer let the nonprofit Mary's Place use an old Travelodge hotel the company owned as a temporary homeless shelter before Amazon would tear down the building for office space, and Bezos personally gave $1 million to the organization. In May, Amazon announced plans to build a permanent homeless shelter for Mary's Place in a new office building under construction. In June, Amazon also said it would give new food-prep and service space in future Amazon buildings and up to $1 million to FareStart, a nonprofit that runs restaurants and catering to train disadvantaged workers for jobs in the food-service industry.In late 2013, the company started AmazonSmile to donate a portion of sales to nonprofits that customers choose. The AmazonSmile Foundation gave away about $13 million in 2015, the last year tax records are available. And it's supported the computer science department at the University of Washington with two endowed million-dollar faculty chairs for professors and $10 million for the university's new Computer Science & Engineering building."If you look at what they have done for the University of Washington and the recent homelessness investment when Seattle has had a serious problem with homelessness, Jeff was involved all the way," says UW's Lazowska. When Lazowska's department was recruiting machine-learning experts Carlos Guestrin and Emily Fox, he emailed Bezos for help to endow professorships to lure them. Lazowska says within 30 minutes of his email, Bezos responded and began the process to hook up Amazon funding, and Bezos also personally met with the two computer scientists to help win them over.Aside from running Amazon, Bezos is devoting attention and money to BlueOrigin, his for-profit space-exploration company. In April, Bezos said he sells about $1 billion of Amazon stock a year to fund the venture. "I believe it's incredibly important that we humans go out into space and the primary reason, if you think long-term about this, is we need to do that to preserve the earth," he told Charlie Rose last year. The goal is long-term, to put it mildly. "What I want to do with Blue Origin is build heavy-lifting infrastructure that lowers the cost of access to space so that the next generation of entrepreneurs can have a dynamic entrepreneurial explosion in space," he said. "That is how we will move all heavy industry into space and then ultimately Earth can be effectively zoned residential and light industrial." Bezos also owns The Washington Post.Bezos appears to be searching for direction to give more personally. In June, he tweeted out what he called "a request for ideas," asking for suggestions on how he should approach philanthropy. He said because he spends so much time thinking about the long term, he's interested in funding projects to help people in the "here and now... at the intersection of urgent need and lasting impact." He cited Amazon's giving to Mary's Place as an inspiration for this approach. In late August, he followed up with a tweet thanking those who responded, saying they had already changed his thinking about his approach. "More to come," Bezos wrote. Raikes, who says he considers Bezos a friend, wrote to Bezos offering to talk through how to think about philanthropy. "If you're too short-term-oriented, you can make the problem worse" by not addressing systemic causes, Raikes says. "If it's near-term investments that help transform the system, then I think that's good."

There's one other adjustment Bezos may need to make. Amazon has a reputation for an aggressive work environment, which can be at odds with the mission-driven motivation that lures people to philanthropy. Raikes says, "Some of the ways in which you manage and lead people in this sector have to be different."