Bill Gates is taking on a bigger role at Microsoft. He's stepping down from his position as chairman today and will take up the role of technology advisor to Microsoft's new CEO, Satya Nadella. "I'm thrilled that Satya has asked me to step up, substantially increasing the time that I spend at the company," Gates says in a video discussing Nadella's new role. "I'll have over a third of my time available to meet with product groups, and it'll be fun to define this next round of products working together."

"The opportunity for Microsoft is greater than ever before."

Though Gates has regularly stated that he'd prefer to spend more of his time working on philanthropic projects than Microsoft, Nadella is said to have requested Gates' assistance while stepping into his new role. Gates says that Nadella has the right background to lead Microsoft forward, explaining that Microsoft has large opportunities ahead of it in mobile and cloud computing — the latter an area that Nadella has plenty of experience in. "The opportunity for Microsoft is greater than ever before," Gates says.

Gates will be succeeded as chairman by John Thompson, who joined Microsoft's board in February of 2012. Thompson is currently the CEO of Virtual Instruments and previously served as CEO and chairman of Symantec. Thompson's appointment also marks a major change for Microsoft: Gates has served as the company's chairman since 1981, well before he stepped down as CEO. The leadership change comes at a critical point for Microsoft, and it's clear that both Gates and Nadella know it. The PC industry is slowing down; now they'll need to help Microsoft find greater success in mobile and the cloud from their new roles.