Early Expansion (IMAGE) University of Pennsylvania School of Medicine Caption Hopx+ cells (green) in the early embryo that are capable of expansion. Red is proliferating cells; blue is nucleus of cells. Credit Courtesy of Deqiang Li, Rajan Jain, Jonathan A. Epstein, University of Pennsylvania 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.