Illustration of the US geneticist Michael Rosbash (born 1944). While studying patterns of activity and rest in fruit flies (Drosophila melanogaster) Rosbash and his colleague Jeffrey C Hall discovered the period gene, a rhythm-regulating gene whose product accumulates during the night and degraded during the day. They went on to discover other rhythm-regulating genes, that were expressed throughout the body, and that responded to different stimuli, such as light. The same self-regulating biological clock has been shown to exist in other animals, including humans. Rosbash and Hall, along with Michael Young (who independently discovered the period gene), were awarded the 2017 Nobel Prize in Physiology or Medicine for their discoveries of molecular mechanisms controlling the circadian rhythm.