Neutrino Mixing: from experiment to theory

In first part of the talk we survey the experimental results on neutrino mixing, review phenomenological mixing patterns and discuss interpretations in terms of deviations from tri-bimaximal mixing, including mixing sum rules. In the second part of the talk we introduce theoretical approaches to neutrino mixing. We first consider the see-saw mechanism with right-handed neutrinos and sequential dominance. We then discuss approaches based on symmetry, in particular both GUT symmetry and discrete family symmetry, in constructing unified models of quark and lepton masses and mixing. Various different approaches to model building are described, denoted as direct, semi-direct and indirect, and the pros and cons of each approach is discussed.