Array (IMAGE) University of Wisconsin-Madison Caption In the lab of William Murphy at UW-Madison, these six experimental samples are substrates that were evaluated for their ability to support stem cells. The samples, each 1 millimeter in diameter, and contain subtle chemical and physical variations, affecting such factors as hardness, speed of breakdown, and points for cellular attachment. Inset shows a network of blood vessels generated for the new Nature Biomedical Engineering paper, based on stem cells that grew on one particular substrate. Credit Credit: William Daly, Eric Nguyen and Mike Schwartz, UW-Madison 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.