Donald Glaser, at the University of Michigan, invents in 1952 a device capable of making the tracks of subatomic particles visible: a vessel filled with liquid — typically liquid hydrogen — kept just below its boiling point via a sudden drop in pressure, so that any charged particle passing through the liquid leaves behind a trail of tiny vapor bubbles along its path, which can be photographed and analyzed with precision. The bubble chamber substantially improves on the cloud chamber invented by Charles Wilson decades earlier, by allowing the use of liquids much denser than water vapor or alcohol, which drastically increases the probability that high-energy particles will interact with the medium and leave analyzable tracks. Built at larger scale by Luis Alvarez at the University of California, Berkeley, the bubble chamber becomes, over the following two decades, the standard experimental tool of particle physics, enabling the discovery of numerous new subatomic particles before being progressively replaced by digital electronic detectors in modern accelerators.