The International Space Station over Earth

Explanation: The International Space Station is the largest object ever constructed by humans in space. The station perimeter extends over roughly the area of a football field , although only a small fraction of this is composed of modules habitable by humans. The station is so large that it could not be launched all at once -- it continues to be built piecemeal . To function, the ISS needs huge trusses , some over 15 meters long and with masses over 10,000 kilograms, to keep it rigid and to route electricity and liquid coolant s. Pictured above , the immense space station was photographed from the now-retired space shuttle Atlantis after a week-long stay in 2010. Across the image top hangs part of a bright blue Earth , in stark contrast to the darkness of interstellar space across the bottom.