Science image (IMAGE) Salk Institute Caption Clusters of long-lived mitochondria in neurons. Older mitochondria (black arrows, in maroon) and younger mitochondria (yellow arrows, in cyan) demonstrating age mosaicism (differential aging) among mitochondria in the brain. Credit Salk Institute Usage Restrictions with credit and related coverage. License Original 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.