ISS Photography By Scott Kelly

Health studies
The International Space Station has developed exercise equipment, including treadmills and resistance devices to limit muscle atrophy in a low gravity environment. Weightlessness causes body fluids in astronauts to accumulate in the upper half of the body, leading to facial edema and unwelcome side effects. Studies on astronauts have suggested that weightlessness leads to vision problems due to increased intracranial pressure changing the shape of the eyeball.