Three American scientists have won the Nobel Prize for Medicine for their discoveries about the body's daily rhythms.

Jeffrey Hall, Michael Rosbash and Michael Young won the nine million kronor (£820,000) prize for isolating a gene that controls the body’s daily rhythm.

These biological inner clocks regulate critical functions such as sleep, behaviour, hormone levels and body temperature.

Professor Rosbash, 74, is on the faculty at Brandeis University. His parents were immigrants from Nazi Germany and his father was a cantor. Thomas Perlmann, secretary at the Karolinska Institute Nobel Committee said that when he told Rosbash about the award, “He was silent and then he said ‘you are kidding me’.”

Dr Young is based at Rockefeller University, while Professor Hall is at the University of Maine.

The Nobel committee’s citation said the three scientists “were able to peek inside our biological clock and elucidate its inner workings.

“Their discoveries explain how plants, animals and humans adapt their biological rhythm so that it is synchronized with the Earth's revolutions.”

Other researchers have found that not just humans, but animals and plants have a biological clock that helps to prepare our physiology for the fluctuations of the day.

This regular adaptation is referred to as the circadian rhythm.