Fragile X (IMAGE) University of Wisconsin-Madison Caption This image from a confocal microcope shows neural stem cells (green) in the mouse hippocampus that are actively proliferating because they express Ki67(red), a protein that is only present in proliferating cells. Credit Yue Li 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.