One of the most important moments in the history of science and technology happened 40 years ago on Thursday.
On 16 July 1969 a space mission called Apollo 11 blasted off from Earth to take men to the moon.
Five days later, two of the men aboard Apollo 11 - Neil Armstrong and Buzz Aldrin - became the first men to walk on the moon.
Millions of people around the world watched the launch, and tuned in again to see Armstrong take the first steps.
As many as a million people travelled to the state of Florida to watch the Apollo mission take off at 9.32am (2.32pm UK time).
Apollo 11 was actually fairly small and was launched into space on top of a huge rocket called Saturn 5.
As well as Armstrong and Aldrin, a third astronaut also blasted into space on Apollo 11 - Michael Collins.
He looked after part of the spacecraft called the command module, which floated in orbit around the moon while Armstrong and Aldrin went to the surface in a smaller craft.
The mission wasn't the first to take men to the moon, but it was the first time a craft with men on board left orbit and landed on the moon.