The International Space Station (ISS) is a modular space station in low Earth orbit, primarily built by the United States and Russia, with contributions from a multinational consortium including the European Space Agency, Japan, and Canada. Its assembly began in 1998 with the launch of the Russian module Zarya, followed by the U.S. module Unity. The ISS has been continuously inhabited since November 2, 2000, serving as a microgravity laboratory for scientific research across various fields, including biology and physics. It is powered by large solar arrays and supports a crew of international astronauts who typically stay for about six months.