Expedition 21 was a mission to the International Space Station (ISS) that took place from November 2009 to March 2010. It involved a crew of six astronauts, including Jeff Williams and Maxim Surayev, who conducted scientific research and maintenance tasks aboard the ISS. The mission aimed to advance knowledge in various fields, including biology, physics, and Earth sciences. During Expedition 21, the crew performed several spacewalks and experiments, contributing to ongoing research in microgravity. They also supported the arrival of the Progress 36 cargo spacecraft, which delivered supplies and equipment to the ISS. The mission played a crucial role in the continuous operation of the space station.