Three Americans — Jeffrey C. Hall, Michael Rosbash and Michael W. Young — have won the 2017 Nobel Prize in physiology or medicine for their work on molecular mechanisms that control circadian systems.

Hall was born in New York, Rosbash in Kansas City, and they both worked at Brandeis University. Michael Young was born in Miami and worked at Rockefeller University.

In announcing the winner in Stockholm on Monday, the prize committee said the men elucidated how a life-form’s “inner clock” can fluctuate to optimize our behavior and physiology. “Their discoveries explain how plants, animals and humans adapt their biological rhythm so that it is synchronized with the Earth’s revolutions.”

Working with fruit flies, the scientists isolated a gene that is responsible for a protein that accumulates in the night but is degraded in the day. Misalignments in this clock may result in medical conditions and disorders, as well as the temporary disorientation of jet lag that travelers experience when crisscrossing time zones.

The circadian clock anticipates and adapts our physiology to the different phases of the day. (The Nobel Assembly at Karolinska Institutet)

The scientists’ paradigm-shifting work revolves around three genes dubbed “period,” “timeless” and “doubletime.”

Their early work took place in 1984 when Hall and Rosebash worked together at Brandeis and Young at Rockefeller University to isolate the “period” gene, which controls the circadian rhythm of fruit flies. Hall and Rosbash then showed that the level of the protein encoded by this gene changes in a 24-hour cycle, going up during the day and down at night. They theorized that this protein blocked the activity of the period gene.

“Since the seminal discoveries by the three laureates, circadian biology has developed into a vast and highly dynamic research field, with implications for our health and well-being,” the Nobel committee explained.