On March 1, 2016, NASA astronaut Scott Kelly came back to Earth after spending almost an entire year at the International Space Station, breaking the record for the longest spaceflight by an American. [‘On This Day in Space’ Video Series on Space.com](https://www.space.com/39251-on-this-day-in-space.html)

He and his Russian crewmate Mikhail Kornienko spent 340 consecutive days at the space station. During that time, Scott Kelly took part in NASA's twins study with his twin brother, Mark. His extended stay in space would help researchers learn about the health effects of long-term spaceflight.