Stream of Sand (IMAGE) U.S. National Science Foundation Caption Low levels of surface tension cause water-like droplet formation in flows of dry granular materials. Credit Helge F. Gruetjen*, John R. Royer, Scott R. Waitukaitis, and Heinrich M. Jaeger, The University of Chicago 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.