  We present a model for the metal-insulator transition in 2D, observed in the
recent years. Our starting point consists of two ingredients only, which are
ubiquitous in the experiments: Coulomb interactions and weak disorder
spin-orbit scattering (coming from the interfaces of the heterostructures in
question). In a diagramatic approach, we predict the existence of a
characteristic temperature $T_o=T_o(n,\omega_H)$, $n$ being the density of
carriers, and $\omega_H$ the Zeeman energy, below which these systems become
metallic. This is in very good agreement with experiments, and corroborates the
fact that varying $n$ and $\omega_H$ are equivalent ways into/out of the
metallic regime. The resistivity, calculated as a function of temperature and
$\om_H$ in the metallic state, compares favorably to experiment. We comment on
the nature of the transition, and calculate the specific heat of the system.
