Number 44 (Story #1), August 8, 1991 by Phillip F. Schewe and Ben Stein IRON HYDRIDES ACTUALLY EXPAND WHEN SQUEEZED to pressures of 3.5 GPa or more. Scientists at the Carnegie Institution of Washington, D.C. (Russell Hemley, 202-966-0334) discovered that under the high pressures of a diamond anvil cell, iron samples immersed in a hydrogen fluid will swell by more than 17% in volume as hydrogen atoms fill up small pockets between the iron atoms. This sponge effect is of interest to materials scientists studying how hydrogen makes metals brittle and to geologists who seek to know whether hydrogen exists at the Earth's core. (Science, 26 July 1991.)