When he was 25, he spent most of the year training for his Vostok 2 orbital flight. On August 6, 1961, a month shy of his 26th birthday, Titov became the second person to orbit Earth, and the fourth to go into space (after Yuri Gagarin and Americans Alan Shepard and Gus Grissom). Titov (with John Glenn and President Kennedy) also became the person with the most time in space (25 hours, 18 minutes), a record that stood for another year, and the first to sleep in space and to get space sick. He died in 2000, and remains the youngest person to travel in space, and the only 25-year-old to go.
Photos from: "What Were They Doing at 25?" »