The International Space Station was a cramped, humid, puny three rooms when the first crew moved in. Twenty years and 241 visitors later, the complex has a lookout tower, three toilets, six sleeping compartments and 12 rooms, depending on how you count. Monday marks two decades of a steady stream of people living there, according to AP. Astronauts from 19 countries have floated through the space station hatches, including many repeat visitors who arrived on shuttles for short-term construction work, and several tourists who paid their own way. The first crew American Bill Shepherd and Russians Sergei Krikalev and Yuri Gidzenko blasted off from Kazakhstan on Oct. 31, 2000. Two days later, they swung open the space station doors, clasping their hands in unity. Shepherd, a former Navy SEAL who served as the station commander, likened it to living on a ship at sea. The three spent most of their time coaxing equipment to work; balky systems made the place too warm. Conditions were primitive, compared with now. Installations and repairs took hours at the new space station, versus minutes on the ground, Krikalev recalled. Each day seemed to have its own set of challenges, Shepherd said during a recent NASA panel discussion with his crewmates. The space station has since morphed into a complex that's almost as long as a football field, with eight miles (13 kilometers) of electrical wiring, an acre of solar panels and three high-tech labs.