In our cells an internal clock helps us to adapt our biological rhythm to the different phases of day and night. Jeffrey Hall, Michael Rosbash and Michael Young studied fruit flies to figure out how this clock works. In 1984 they managed to identify a gene that encodes a protein that accumulates during the night but is degraded during the day. They also identified additional proteins that form part of a self-regulating biological clockwork in the fruit fly's cells. The same principles have been shown to apply to other animals and plants.