It's been three years since the first human inhabitants took up residence aboard the International Space Station (ISS). Since then, the ISS has been home to eight resident crews who have performed fantastic research in the microgravity of Earth orbit. But none of this would have been possible without America's first space station: Skylab.

From its launch on May 14, 1973, until the return of its third and final crew on Feb. 8, 1974, the Skylab program proved that humans can live and work in outer space for extended periods of time.

Skylab served as the greatest solar observatory of its time, a microgravity lab, a medical lab, an Earth-observing facility, and, most importantly, a home away from home for its residents. The program also led to new technologies. Special showers, toilets, sleeping bags, exercise equipment and kitchen facilities were designed to function in microgravity.