Multipass amplifier (IMAGE) University of Tokyo Caption This eerie green glow comes from the amplification of laser light used to cool positronium. Credit ©2024 Yoshioka et al. CC-BY-ND Usage Restrictions Credit must be given to the creator. No derivatives or adaptations of the work are permitted. License CC BY-ND 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.