On Feb. 19, 1986, the Soviet Union launched the Mir space station. While this wasn't the first space station launched into orbit, it was the first one that had to be assembled piece-by-piece in space.
Mir enabled the first long-duration human spaceflight missions. The current record for the longest stay in space was set aboard the Mir space station by cosmonaut Valeri Vladimirovich Polyakov, who spent 437 consecutive days in orbit.
The Soviets used Mir to do all kinds of scientific research for 15 years before funding for the program was cut, and Mir fell back to Earth, burning up in the atmosphere along the way.
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Catch up on our entire "On This Day In Space" series on YouTube with this playlist.
Email Hanneke Weitering at hweitering@space.com or follow her @hannekescience. Follow us @Spacedotcom and on Facebook.