  An elementary general overview of the neutrino physics and astrophysics is
given. We start by a historical account of the development of our understanding
of neutrinos and how they helped to unravel the structure of the Standard
Model. We discuss why it is so important to establish if neutrinos are massive
and we introduce the main scenarios to provide them a mass. The present bounds
and the positive indications in favor of non-zero neutrino masses are discussed
as well as the major role they play in astrophysics and cosmology.
