False-colour streamer chamber photo of a pion- muon- electron (pi-mu-e) decay chain resulting from an antiproton annihilation. The antiproton enters from the bottom of the picture & annihilates with a proton in neon gas filling the chamber; their energy materialises as 3 nuclear fragments (thick tracks) & several positive & negative pions (less dense tracks). One positive pion curls tightly to the right in the chamber's magnetic field before decaying to a muon; the muon forms the spiral at top & then decays in turn to an electron. At each decay the tracks change direction sharply, indic- ating simultaneous emission of an unseen neutrino. Photo taken at Experiment PS 179 at CERN, Geneva.