ISS above Earth in 2000

This week marks the 10th anniversary of a milestone in space exploration.

Since the year 2000, the International Space Station has been continuously occupied. Constant human presence aboard the space station--an outpost one official has called the "zero gravity United Nations"--has been an unparalleled global success, from both a scientific and cultural standpoint.

More than 200 orbiting explorers have visited the space complex; 15 nations have contributed to the missions, providing modules and hardware; and more than 600 experiments have been carried out on board. The exploration outpost has served as a symbol of international cooperation and worldwide unity.

This image, taken in September 2000, shows the growing space station, which would soon expand, becoming occupied just weeks later after the Russian launch on October 31 and subsequent docking on November 2.