The Osmio seal was inspired by this photograph of a “diamond anvil,” used with the kind permission of the Carnegie Institution of Washington. As reported in Physical Review Focus, it shows a sample of the elemental metal osmium being squeezed under 600,000 atmospheres of pressure on an anvil (two diamonds separated by a thin metal gasket with a hole in the center) by Hyunchae Cynn and his colleagues at the Lawrence Livermore National Laboratory in California. The anvil’s hole is filled with osmium powder; argon was added to distribute the pressure evenly. X-ray diffraction patterns show the spacing between osmium atoms in the sample at different pressures. The result: osmium’s bulk modulus of 462 GPa means that it holds up to pressure better than any other known substance. It is stiffer even than diamond, whose bulk modulus is a mere 443 GPa.