Having successfully launched and docked, astronauts on board China's Tiangong-1 space lab are beginning their scientific experiments.

Over a period of up to 20 days the crew will perform a variety of tasks designed to get them used to life in space, as well as preparing China for eventually building a full size, full time space station.

Top of the list is learning about physiology and keeping fit in space.

With nothing to weigh the human body down, muscle mass quickly degenerates in orbit, meaning astronauts need to keep moving in other ways. The crew of Tiangong-1 have an exercise bike, as well as various coordination developing exercise equipment.

This mission, the first to the lab, is primarily medical with later missions likely to focus on other areas.