Human Endothelial Stem Cells (IMAGE) Rice University Caption Green fluorescent tags in a colony of human endothelial stem cells show high activity as they organize themselves into a pattern 40 hours after the BMP4 signaling pathway is activated. Rice University biosciences carried out experiments on contained colonies of cells to learn new details about how they're triggered to differentiate in embryos. Credit Warmflash Lab/Rice University Usage Restrictions Credit must be used. 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.