This year’s Nobel Prize in medicine has been awarded to three scientists who discovered the genes that control the circadian rhythm, or the body’s natural day-night cycle.

All three winners are American, and all three based their work on fruit flies. Michael Rosbash and Jeffrey Hall collaborated at Brandeis University to isolate the “period gene” that is key to regulating the circadian rhythm. (Rosbash is still at Brandeis; Hall is now at the University of Maine.) This gene encodes for a protein that builds up at night and then degrades during the day; different levels of the protein affect how our body adapts to different times of day.

The third winner, Michael Young of Rockefeller University, worked independently. He discovered the “timeless gene,” which produces proteins necessary to stop the activity of the period gene. The findings of all three were published in the 1980s.

These discoveries allow us to “peek inside our biological clock,” according to the Nobel Prize committee. In humans, the circadian rhythm has been linked to the workings of our metabolism, jet lag, and the sleep cycle. But it also exists in plants, where it affects the growth rate of crops, for instance. In a 2014 interview with the Howard Hughes Medical Institute Bulletin, Rosbash said that “the circadian system has its tentacles around everything.” Because everything on Earth is affected by the Sun, the circadian rhythm is “ticking away in almost every tissue in the human body.”

The three winners will split a prize of roughly $1.1 million, and receive medals engraved with their names. Last year’s prize was awarded to Yoshinori Ohsumi for his research on cells that eat themselves.