This book reviews the recent achievements in neutrino physics over the last two decades, ranging from the first experiments on nuclear beta-decay, that have brought to its discovery, up to the newest terrestrial experiments and cosmological measurements. In particular, it provides a summary of the properties of neutrinos in and beyond the Standard Model, it treats of the neutrinos masses, of the double beta-decay, and neutrino oscillations, and at last, it focuses on the study of extraterrestrial neutrinos of different origins: atmospheric, solar, and cosmogenic.