  Lopsided structure in mass matrices of down quarks and leptons gives a simple
explanation for the observed large angles of neutrino mixings. We realize such
mass matrices by the Froggatt-Nielsen mechanism in the framework of
supersymmetric SO(10) grand unified theory (GUT). It is shown that the model
can reproduce the successful mass matrices which have been obtained in SU(5)
models. Cosmological implication of the model is also discussed. We show that
the hybrid inflation occurs naturally in the model and it offers non-thermal
leptogenesis by decays of the next-to-lightest right-handed neutrinos. The
present baryon asymmetry is explained by just the oscillation mass scale in the
atmospheric neutrinos.
