Virtually anyone who made it to the top started at, or somewhere very near, the bottom. The vast majority do a fair bit of wandering around before arriving at the corner office, changing jobs, or even careers, more than once. But some made their transition without ever changing employers—they walked in the door as an intern or mailroom employee and ended up running the show. For students now starting their summer internships, the notion that a temp job could somehow lead to the very pinnacle of corporate power is no doubt a comforting one, even if lottery tickets would give them a better chance of hitting it big. What follows are 20 people who started at the bottom and ended up at the very top.