Tapped to reboot Microsoft, 46-year-old Satya Nadella took over as the company’s third CEO on Feb. 4. “Many who know me say I am also defined by my curiosity and thirst for learning. I buy more books than I can finish. I sign up for more online courses than I can complete,” Nadella wrote to employees on his first day as CEO. “I fundamentally believe that if you are not learning new things, you stop doing great and useful things.” Nadella has been with the company for 22 years, notably heading up development of the Bing search engine, then its server and tools division, and most recently as EVP of cloud and enterprise.