Strong evidence for neutrino oscillation came in 1998 from the Super-Kamiokande collaboration in Japan. It produced observations consistent with muon neutrinos (produced in the upper atmosphere by cosmic rays) changing into tau neutrinos within the Earth: Fewer atmospheric neutrinos were detected coming through the Earth than coming directly from above the detector. These observations only concerned muon neutrinos. No tau neutrinos were observed at Super-Kamiokande. The result made it, however, more plausible that the deficit in the electron-flavor neutrinos observed in the (relatively low-energy) Homestake experiment has also to do with neutrino mass.