Shortly after being named the 2002 TR100 Innovator of the Year, Max Levchin left PayPal, the company he had cofounded, which he and his partners sold to eBay for more than $1.5 billion. About a year later, he founded Slide, a company that creates playful ways to showcase photos on home pages, blogs, and social-­networking websites like Facebook. Slide is currently one of the most ­popular services of its kind, allowing the images of more than 120 million users to swirl, revolve, fade, or "steam" into existence somewhere on Web.

Technology Review: If you were able to give your 26-year-old self any advice, what would you say?