In the last few years, Tumblr has become one of the most popular social networking websites. Before Tumblr was the company we know today, however, it was just one of David Karp's smaller projects. Learn more about one of the most successful young people working in tech—and how he changed the way people share who they are and what they like. Discover the story behind David Karp's success—and find out what it takes to turn a new company into something amazing.