The Photosystem II Crystal (IMAGE) Max-Planck-Gesellschaft Caption The photosystem II crystal (center of image) is smaller than the head of a pin. In order to position it better, the scientists irradiate it with green light. Helium flowing in from above cools it to minus 260 degrees Celsius. The highly-pulsed and polarised X-ray hits the sample from bottom right. The tip of the EXAFS detector, which is equipped with 30 elements, protrudes from the left edge. Credit Johannes Messinger -- MPI for Bioinorganic Chemistry 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.