Microscopic Hair Spheres (IMAGE) University of Pennsylvania School of Medicine Caption Hair spheres formed by proliferation of multipotent stem cells derived from human hair follicles. Credit Xiaowei Xu, University of Pennsylvania School of Medicine and the American Journal of Pathology Usage Restrictions None 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.