Vitalik Buterin

Buterin describes his open-source blockchain platform Ethereum as a “world computer.” The skinny visionary’s experiment, which began as a white paper, now has a market valuation of about $48 billion, making it the second-most-valuable crypto network next to Bitcoin. Ethereum caught a lucky break this year when the SEC said it would not regulate Ether, the network’s native coin, as a security. Rumor has it Google recently tried to hire Buterin to lead its own whispered crypto endeavors, but he declined. (Also No. 22 on the main Fortune 40 Under 40 list.)