 Mao is one of the most prolific users of the diamond anvil cell for research at high pressures.Although at the time the claim was controversial, his work with Peter M. Bell is now generally accepted as being the first verified static pressure in excess of 1 Megabar.In 1987, Mao and a colleague at the Geophysical Laboratory, Robert Hazen, identified the composition and structure of the first high-temperature superconductor to have a critical temperature above the boiling point of liquid nitrogen.