Astronaut holding a tissue chip during a space walk. This chip is part of research into the human immune system and aging on the International Space Station. The chip carries three types of cell to model aspects of the human immune system. The microgravity conditions that astronauts are exposed to on space missions have been shown to cause physiological changes that are normally associated with aging, including altered immune systems. The changes are mostly reversed on return to Earth. Studying these changes could lead to ways to slow the aging process on Earth. Photographed on 6th July 2018.