The International Space Station (ISS) is celebrating its 15th birthday. Its first component was launched into space from Russia on November 20, 1998. Since then, it's had an incredible ride.
Turning 15 is a big deal in anyone's book. And it's no different for the International Space Station, which is celebrating the day it was launched into space in 1998.
It was another two years before the first crew arrived to live at the station in November 2000. Since then, the ISS has been occupied without interruption for 13 years – it's the longest continuous human presence in space. In total, 211 people have worked on, or visited, the ISS.
One of them is astronaut Thomas Reiter. He spent 171 days on the ISS in 2006.
Reiter was the first German on the ISS and still talks about his experience of working with his international colleagues with reverence: "Thousands of engineers and scientists are working together on mankind's largest science project – that only works when you understand each other."
But the most mundane things can be quite difficult when you're on the world's biggest science project.
For instance, because of the absence of gravity, astronauts have to wrap their legs around the toilet bowl when they need to go. And alcohol is completely forbidden because its effects on the human body are intensified by the weightlessness of space.
The perfect laboratory
Five space agencies are involved with the project: The American National Aeronautics and Space Administration (NASA), the European Space Agency (ESA), the Canadian Space Agency, the Japan Aerospace Exploration Agency and the Russian Federal Space Agency, Roscosmos.
Scientists at ESA say the ISS is the perfect place "for studying Earth and its climate, the sun and its varying characteristics, and all the particles and radiation coming from the whole universe."
The ISS circles the earth at an incredible speed of more than 27,000 kilometers per hour.
And it's been known to welcome strange objects - such as the Olympic torch for the 2014 Winter Games in Sochi, Russia. While other Olympic torches have been on American space shuttles, the Sochi torch was the first to be taken on a space walk outside the ISS. But it was kept unlit during the entire trip.
The next European mission to the ISS is scheduled for May 2014.
It's hoped the young German astronaut Alexander Gerst will be one of those flying into space. He will have a new tool with him to study how metallic mixtures react to weightlessness, and he will take part in the ISS's ongoing life-science research projects.