1 v 1 3 1 D ec 2 00 3 Neutrinos : Windows to Planck Physics ∗

After recalling some elegant contributions of the late Freydoon Mansouri, we turn to neutrino physics and use a modicum of grand unification to relate quark and lepton mixing matrices. We advocate an expansion for the MNS matrix, à la Wolfenstein, and argue that in a wide class of models, θ13 is a Cabibbo mixing effect. Also the large neutrino mixing angles reflect the mass patterns of the righthanded neutrinos near the Planck scale, and provide evidence for family structure at that scale.