Even space stations need their windows cleaning, but it's a big task when you're floating in space.
Two Russian cosmonauts aboard the International Space Station (ISS) took a spacewalk to clean a porthole window, 250 miles above the Earth's surface.
The window had gathered years of dirt left by the exhaust fumes of visiting spaceships.
As well as giving the porthole a clean, the cosmonauts also installed new equipment and carried out maintenance outside the station,
It took them six hours to complete the job.
It was the fourth spacewalk on the ISS this year, and the tenth one for station commander, Gennady Padalka, who holds the record for the most time any person has spent in space.