The International Space Station (ISS) is a large spacecraft that orbits Earth at an average altitude of 400 kilometers (250 miles). It serves as a unique laboratory for scientific research in a microgravity environment, enabling experiments in fields like biology, physics, and astronomy that aren't possible on Earth. The ISS is a joint project between space agencies such as NASA (USA), Roscosmos (Russia), ESA (Europe), JAXA (Japan), and CSA (Canada). Since its first module was launched in 1998, the ISS has been continuously inhabited by astronauts, serving as a symbol of international cooperation in space exploration.