Three American researchers have been awarded the the Nobel Prize for Medicine for discoveries about circadian rhythms -- the daily workings of the human body.
The winners are Jeffrey Hall, Michael Rosbash, and Michal Young, the Karolinska Institute in the Swedish capital, Stockholm, announced on October 2.
Robash is on the faculty at Brandeis University in Massachusetts, Young at Rockefeller University in New York, and Hall is at the University of Maine.
The citation for the 9 million kronor ($1.1 million) prize says the scientists isolated a gene that controls the normal daily biological rhythm.
They "were able to peek inside our biological clock and elucidate its inner workings," the citation said.
Circadian rhythms adapt one's physiology to different phases of the day, influencing sleep, behavior, hormone levels, body temperature, and metabolism.
Hall, Rosbash, and Young have conducted research into sleep patterns since the 1980s.
The recipients of prizes in physics, chemistry, and peace will also be announced during the upcoming week.
The winner in economics will be announced next week, likely on October 9.
The most-watched Nobel is the Peace Prize, the only one presented in the Norwegian capital, Oslo. It is expected to be announced on October 6.
Some have suggested the award could go to the organizers of the July 2015 deal between Iran and global powers in which Tehran agreed to curtail its nuclear activities in exchange for relief from international sanctions.
If so, Iranian Foreign Minister Mohammad Javad Zarif and EU foreign policy chief Federica Mogherini would be contenders for the prize, observers say.
The United States and other Western governments fear that Iran is seeking to develop nuclear weapons. Tehran says its nuclear program is intended solely for peaceful purposes including power generation.
Also believed to be contenders are Syria's White Helmets rescue service, Congolese doctor Denis Mukwege, jailed Saudi blogger Raif Badawi, and Edward Snowden, who revealed details of the NSA electronic surveillance program in the United States.