Morgan Sherwood (flawedartist) from San Francisco (CA), USA · CC BY 2.0

Max Levchin arrived in the United States from Kyiv in 1991 and, in 1998, co-founded the security startup Confinity with Peter Thiel — the company that became PayPal after merging with X.com. As chief technology officer he built PayPal's anti-fraud systems and co-created the Gausebeck-Levchin test, one of the first commercial CAPTCHA implementations, a piece of the everyday internet now used by nearly every website that needs to tell a human from a bot. After eBay acquired PayPal in 2002, he went on to found the buy-now-pay-later lender Affirm, which he still leads as CEO.