A diamond anvil cell works by placing carved diamonds on the tips of piston cylinders so that the force of compression is concentrated over a very small area, and pressures of up to 2 Mbar of pressure may be achieved (the pressure at the center of the Earth is 1.3 Mbar!). At this pressure, however, the diamonds frequently shatter, so much lower pressures are routine. The pressure is measured by observing the fluorescence properties with a ruby laser.