A return to the Moon, Mars expeditions, and a rise in space tourism will lead to an increasing number of human spaceflights. The ‘Gravitational biology and space medicine’ Collection focuses on the challenges to the health of humans in space during long-term space missions and the physiological changes during short-term altered gravity conditions, the possible influence of space radiation, available countermeasures and possible applications on Earth. In addition, studies reporting on in vivo changes in space-flown mice were published. Finally, this Collection also brings together articles reporting experiments using cells cultured under conditions of real microgravity on the International Space Station, or exposed in ground-based facilities, in order to study morphological and molecular alterations in different cell types.