Who first observed liquids crystallizing under high pressure?

In 1963, the scientist Alvin Van Valkenburg became the first person to observe liquids, such as water and alcohol, crystallize under high pressure.1

This observation was made possible through his work with the diamond-anvil cell, an apparatus that allows researchers to visually observe the effects of pressure on samples confined between two gem-quality diamonds. By placing a thin metal foil gasket between the diamond-anvil faces, Van Valkenburg was able to create a sample chamber that successfully contained fluid samples for high-pressure study.1