Neutrinos as elementary particles known as leptons. Currently there is 3 known neutrinos; electron, Muon and Tau neutrino. They also have 3 corresponding anti-neutrinos. Neutrinos react via the weak and gravitational force. Their mass is as of yet unknown, but there are very good estimates on the relative differences in mass between the 3 types of neutrinos. Some of the more famous neutrino experiments include SNO (Canada), Super-Kamiokande (Japan), MiniBooNE (USA), etc.