  We adopt a bottom-up approach to reconstruct the possible neutrino mass
matrix patterns, in the hypothesis that $\lambda = \sin \theta_C$, where
$\theta_C$ is the Cabibbo angle, is a useful expansion parameter in the
neutrino sector as it is in the quark sector. A numerical analysis of these
Cabibbo structures shows that an inverted hierarchy spectrum is statistically
favored by the neutrino oscillation data. We then discuss how apparently
conflicting mass and mixing data for quarks, charged leptons and neutrinos can
fit in a unified perspective. We show that large mixing angles can appear
through the seesaw mechanism, even if the neutrino Dirac mass matrix has
hierarchical eigenvalues and small mixing angles. Finally, it is shown that the
form of the heavy Majorana mass matrix may point towards theories with
extra-dimensions.
