The neutrino was postulated 70 years ago by Pauli  to solve a problem in beta decay and the electron neutrino was experimentally discovered 45 years ago by Reines and Cowen.  Today the Standard Model (of High Energy Physics) includes three distinct types of neutrinos. Experimental evidence will be summarized that indicates that these neutrinos can oscillate among themselves and hence have mass.  Future experiments will be discussed that will address various questions that
are open.