Sunset from space. Clouds illuminated by the glow of the setting Sun shining through the atmosphere of the Earth. The atmosphere separates the Earth (bottom, dark) from space (top, dark). Clouds form mostly in the lowest part of the atmosphere, named the troposphere. The troposphere thickness ranges from 7-25 kilometres. The next layer is called the stratosphere, and ends at a height of around 50 kilometres. Above these layers, the ever-thinning atmosphere fades into the darkness and vacuum of space. Photographed by the Expedition One crew of the International Space Station (ISS) that manned the ISS from 2 November 2000 to 18 March 2001. The ISS orbits 350 kilometres above the Earth.