Human Fibroblast (image) University of California - San Diego Caption This is a confocal micrograph of a primary human fibroblast cell grown in culture stained blue for actin, a highly abundant protein that makes up the cytoskeleton of cells. Energy-producing mitochondria are shown in green. Credit Image courtesy of Matthew Daniels, University of Oxford and Wellcome Images. Usage Restrictions None 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.