Phosphorescent Crystals (IMAGE) University of Michigan Caption U-M researchers have developed pure organic phosphorescent crystals. Here, they glow yellow and green when triggered by ultraviolet light. Credit Marcin Szczepanski, U-M College of Engineering 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.