2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/46928Astrophysical and cosmological arguments and observations give us the most restrictive constraints on neutrino masses, electromagnetic couplings, and other properties. Conversely, massive neutrinos would contribute to the cosmic dark-matter density and would play an important role for the formation of structure in the universe. Neutrino oscillations may well solve the solar neutrino problem, and can have a significant impact on supernova physics.11 pages, REVTEX, figures embedded. Minor update of my contribution to the Proceedings of the Summer School on Physics with Neutrinos (Zuoz, Switzerland, August 4-10, 1996), ed. by M.P.Locher (PSI, Villingen, 1996)High Energy Physics - Phenomenologytext