This book aims to provide a modern description of the Standard Model and its main extensions from the perspective of neutrino physics. In particular it includes a thorough discussion of varieties of seesaw mechanism, with or without supersymmetry. The existence of the latter is suggested by the need to give a justification for the mechanism of spontaneous gauge symmetry breaking responsible for generating particle masses. It also discusses schemes where neutrino mass arises from lighter messengers, which might be lie within reach for the world's largest particle accelerator, the Large Hadron Collider. This book stresses the role of neutrinos for two reasons. First, due to the fact that neutrino properties may serve as a guide to the correct model of unification, hence for a deeper understanding of High Energy Physics, second, because neutrinos play an important role in Astroparticle physics and cosmology. Each chapter will include summaries and set of problems, as well as further reading. Appendices will include useful tables, and equations,