The US space agency, Nasa, is celebrating 50 years since the first orbit of the Earth by an American.
John Glenn piloted the space capsule Friendship 7 into orbit on 20 February 1962.
He then circled the globe three times in five hours.
The former astronaut, who's now 90, celebrated the anniversary by chatting to the crew currently on the International Space Station, a science laboratory floating in space.
Though the Russian, Yuri Gagarin, became the first person in Space in 1961, John Glenn's mission was still a big deal.
Dan Burbank, who's currently aboard the International Space Station, said it "Paved the way for America to become a space power and to go to the Moon and to do the things that we're doing right now...''
In 1998, at the age 77, John Glenn went back into orbit, onboard the shuttle Discovery. He is still the oldest person to have gone to space.