The International Space Station is the largest and most complex international scientific project in history. More than four times as large as the Russian Mir space station, the completed International Space Station will have a mass of about 1 million pounds. It will measure about 360 feet across and 290 feet long, with almost an acre of solar panels to provide electrical power to six state-of-the-art laboratories.

The International Space Station will establish an unprecedented laboratory complex in orbit. Scientists on ISS will study many things, ranging from crystal growth to Earth observation. An important subject of research will be the human body in zero-g (or, more accurately, microgravity&emdash;even in orbit, there is a very slight gravitational pull). What happens to muscles, the heart and arteries, and bones in this microgravity environment? Such studies will improve our understanding of the human body, helping us treat common problems on Earth while preparing for long-term human space exploration like a Mars mission.

Learn more about the International Space Station on NASA's Web site.