Abstract
Scientists in the Crystallography Section at NIST/NBS made several outstanding contributions which greatly promoted the development and advancement of high pressure x-ray crystallography during the second-half of the 20th century. These milestone achievements or "firsts" included: (1) the invention of the lever-arm type diamond anvil cell (DAC) in 1958; (2) the development of DAC technology for powder x-ray diffraction at high pressure in 1960; (3) the introduction of DAC methodology for single crystal x-ray diffraction at high pressure in 1964; (4) the invention of the optical fluorescence ruby method of pressure measurement in 1971; and (5) the discovery of hydrostatic pressure-transmitting media useful to unprecedented pressures for that time. These achievements provided the spark that ignited the explosion of activity in high pressure research that occurred in laboratories throughout the world during the latter part of the 20th century. It is still going on, unabated, today. An estimated 5000 DACs were built during the last 40 years.