(CNN) — “That’s one small step for man, one giant leap for mankind.”

The immortal words of astronaut Neil Armstrong spoken 51 years ago this Monday. It was July 20, 1969, at 10:56 p.m., Armstrong plants the first human foot on the moon.

With an estimated 600 million people around the world watching on TV, he climbs down the ladder and proclaims those unforgettable words.

Moments later, Buzz Aldrin joins him and describes the moon’s surface as “magnificent desolation.” They explore the surface for two and a half hours, collecting samples and taking photographs.

The two left behind an American flag, a patch honoring the fallen apollo one crew, and a plaque that reads, “Here men from the planet earth first set foot upon the moon. July 1969 AD. We came in peace for all mankind.”