▪ Abstract  We review the present state and future outlook of our understanding of neutrino masses and mixings. We discuss what we think are the most important perspectives on the plausible and natural scenarios for neutrinos and attempt to throw light onto the flavor problem of quarks and leptons. This review focuses on the see-saw mechanism, which fits into a big picture of particle physics such as supersymmetry and grand unification, providing a unified approach to the flavor problem of quarks and leptons. We argue that, in combination with family symmetries, this may be at the heart of a unified understanding of the flavor puzzle. We also discuss other new physics ideas, such as neutrinos in models with extra dimensions, and possible theoretical implications of sterile neutrinos. We outline some tests for the various schemes.