The Nobel Prize for Medicine has been awarded to three American researchers for discoveries about the body's daily rhythms.
The laureates are Jeffrey Hall, Michael Rosbash and Michal Young.
Mr Robash is on the faculty at Brandeis University and Mr Young is at Rockefeller University, while Mr Hall is at the University of Maine.
The citation for the nine million kronor prize said the researchers isolated a gene which controls the normal daily biological rhythm, or circadian rhythm.
They "were able to peek inside our biological clock and elucidate its inner workings".
Circadian rhythms adapt a person's physiology to different phases of the day, influencing sleep, behaviour, hormone levels, body temperature and metabolism.