A lepton event, CERN, 1990s.

A lepton event (a neutrino interacting with an electron and emerging as a neutrino); the first observation of 'neutral currents' in the Gargamelle heavy liquid bubble chamber. Here, detectors are used to measure properties of particles; some measure the tracks left behind by particles and others measure energy. Founded in 1954, CERN is the world's leading particle physics research laboratory, and one of Europe's first joint ventures.