Monday 2 November 2015 is an important milestone in the history of space exploration.
It marks 15 years of astronauts continuously living on board the International Space Station.
The ISS was launched back in 1998, but it was another two years before astronauts went to live there.
Since then, there has always been someone staying at the station up in space.
The ISS has become an important place to carry out tests and research that will help future space missions to places like the Moon and Mars.
But it also helps people working in science and technology here on earth.
To celebrate the anniversary Newsround takes a detailed look at the ISS in numbers!
The ISS in numbers
- 357ft is the length of the ISS from end-to-end - that's about the same as a football pitch.
- 2 - After the moon, the ISS is the second brightest object in our night sky. You don't even need a telescope to see it zoom over your house.
- 5 - miles per second, that's the speed at which the ISS travels. It orbits the earth every 90 minutes.
- 220 people from 17 different countries have visited the ISS since it launched.
- 2 bathrooms on board! There's also 1 gym, and a 360 degree bay window.
- 189 spacewalks have taken place from the ISS, totalling up to 1184 hours by 121 different astronauts.
- 52 computers control all the systems on the station.
- 420,000kg is the approximate weight of the ISS - that's about the same as 320 cars.
- 250 miles - the distance the station is from earth.
- 2020 is the year that it is currently planned to be decommissioned - that means it will not be used anymore.