The International Space Station celebrates 15 years of hosting astronauts.

In 2000, the ISS received its first tenants – including NASA Astronaut William Shepard.

Since then, the orbiting has allowed astronauts to perform experiments in micro-gravity not possible on the ground.

Speaking from the Station, Astronaut Scott Kelly says working on the I-S-S helps NASA plan for missions to asteroids and Mars.

“What we’ve learned from this space station that is very important to our future exploration beyond our local environment here, beyond low earth orbit,” says Kelly.

The space station began as a modest two capsules – one from the US, the other from Russia – docked in orbit. Now, the station is nearly the size of a football field, with modules from Japanese, European, and Canadian space agencies.