The phenomenon of neutrino oscillations implies that neutrinos do have a tiny but non-zero mass. I review the evidence for this quantum mechanical process and discuss our present knowledge of the parameters in the neutrino sector. The fact that neutrinos have mass requires a modification of the Standard Model of particle physics. Generically neutrinos indicate the presence of a new fundamental energy scale in the Standard Model, whose value is - however - completely unknown. I will also comment on phenomenological searches for manifestations of new physics in the neutrino sector.