Bridgman's high-pressure atomic destructibility and its growing legacy of ordered states

In 1927 P W Bridgman proposed that the otherwise stable structure of atoms could be broken down in the condensed state of matter by mutual encroachment of neighbouring atoms, this being brought about by pressure. Bridgman's principle of destructibility on systematic densification applies equally to molecular systems and from the modern perspective the aftermath of Bridgman's insight is to be sought in structural transitions, in the ensuing but intertwined re-arrangement of electronic states, and generally in the appearance of quite new states of order, both classical and quantal. This pathway is developed in a brief retrospective with examples drawn from hydrogen and light elements, as well as specific hydrogen-rich systems which, as with hydrogen itself, may also offer the prospect of high-temperature superconductivity.