It began as an audacious idea: to establish a permanent human presence in the most hostile environment known to man - space. It's a dream that would bring together two former Cold War enemies and lead to the most expensive structure ever built. Discover the inside story of the International Space Station. See how NASA engineers triumphed over decades of seemingly insurmountable obstacles to develop Skylab, Space Station Freedom, and finally, the International Space Station. The ISS became humanity's first permanent outpost in space and the largest space structure ever created.