ESA astronaut Tim Peake working with the Minus Eighty Laboratory Freezer for International Space Station (MELFI) during his six-month space mission Principia.The freezer is used to store samples until they are returned to Earth for analysis by researchers. An astronaut typically stores regular samples of blood, saliva, urine and faeces during a mission so researchers can monitor how their bodies adapt to living in space.Follow Tim Peake and his six-month Principia mission via timpeake.esa.