Pink Crystal (IMAGE) University of Southern Denmark Caption The new crystalline material changes color when absorbing or releasing oxygen. Crystals are black when they are saturated with oxygen and pink when the oxygen has been released again. Credit University of Southern Denmark 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.