In 2007, when others his age were studying for midterms and living on dorm food, David Karp was busy launching Tumblr ^[1], an easy-to-use blogging platform that now hosts 17.5 million blogs and receives about 1.5 billion page views per week. The company has also attracted some $40 million in venture funding.

Karp, 24, is used to doing his own thing. At 11, he taught himself how to write code. At 15, he dropped out of high school. A year later, he got a job as CTO of UrbanBaby, a New York City parenting site. At Tumblr, Karp likes to spend his time sketching ideas in notebooks, lunching as a group with his 30 employees, and of course, perusing blogs on Tumblr. One thing he doesn’t like is being pinned down. That quickly becomes clear if you try to make an appointment with him. Or happen to spot him zipping around New York City on his Vespa.

Check out his favorite tech tools ^[2] and read more about the way David Karp works ^[3].