27 amazing photos that show what it was like to work for NASA throughout the years

There are only 45 active NASA astronauts in the world today — and fewer than 300 former ones since the organization's inception in 1958.

But it's a highly sought-after job.

In 2016, a whopping 18,300 people applied for the 2017 astronaut class. Only eight to 14 people will be selected, making the acceptance rate less than .08%. (By comparison, Harvard — one of the most competitive universities in the world — accepted 5.9% of its applicants in 2014.)

To see what it's like to be part of this exclusive group, we sifted through hundreds of photos of NASA astronauts throughout the years. We also found images of people in other roles at NASA, like researchers and administrators.

Below are 27 incredible photos of NASA astronauts and employees dating back to 1959:

SEE ALSO: What it's really like to be a NASA astronaut

A researcher checks on Sam, a Rhesus monkey who rode on a Little Joe spacecraft and experienced three minutes of weightlessness in 1959. Test animals were often used during Project Mercury.

In 1961, Dean Sheibley and Barbara Johnson perform studies in NASA's now-defunct Plum Brook Reactor Facility's chemistry lab — the organization's first and last nuclear reactor.

Former US president Harry S. Truman stopped by NASA headquarters in Washington, D.C. on November 3, 1961. Former NASA administrator James E. Webb gave him a tour and a collection of rocket models for his presidential library.