First satellite with a human on board: Vostok 1 (1961) Soviet cosmonaut Yuri Gagarin became the first person to fly in space on April 12, 1961, achieving three orbits before returning to Earth. This milestone is celebrated worldwide as "Yuri's Night" every year on the anniversary of his flight.

At the time of his flight, Gagarin's mission was seen in the context of the space race between the United States and the Soviet Union. Decades on, however, the mission represents the day that space opened up to humans — humans that eventually participated from numerous countries around the world. More than 500 people have now flown into space, and this number could expand quickly when private space companies begin sending paying customers aloft.