The Circadian Clock (1 of 2) (IMAGE) Salk Institute Caption The circadian clock depicts a person's regular physiological events during certain hours of the day. Credit Courtesy of Salk Institute for Biological Studies Usage Restrictions News media reproduction to illustrate this story permitted with proper attribution as provided above. For one time use only. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.