The out-of-control 40-foot long Tiangong-1, or "Heavenly Palace," is one of China's highest profile space projects. The unmanned space lab was launched in September 2011 as a prototype for China's ultimate space goal: a permanent space station that is expected to launch around 2022.
But the Chinese government told the United Nations in May 2017 that its space lab had "ceased functioning" in March 2016, without saying exactly why.
The incident was embarrassing for China's space program but it hasn't delayed its progress. In September 2016, China launched its second space lab, Tiangong-2.
While it is not uncommon for debris such as satellites or spent rocket stages to fall to Earth, large vessels capable of supporting human life are rarer.
NASA's first space station, Skylab, fell to Earth in an out-of-control re-entry in 1979, burning up harmlessly in the process.
The last space outpost to drop was Russia's 135-ton Mir station in 2001, which made a controlled landing with most parts breaking up in the atmosphere.