  Recent experiments on the two dimensional electron gas in various
semiconductor devices have revealed an unexpected metal-insulator transition
and have challenged the previously held assumption that there is no such
transition in two dimensions. While the experiments are still at the stage of
rapid development, it is becoming evident that they cannot be understood from
the conventional perspective of weak interactions. In the present paper, we
propose the following. (1) The low-density insulating state is the Wigner
Glass, a phase with quasi-long-range translational order and competing
ferromagnetic and antiferromagnetic spin-exchange interactions. (2) The
transition is the melting of this Wigner Glass, disorder being the agent
allowing the transition to be second order. (3) Within the Wigner Glass phase,
there are at least two, distinct magnetic ground-states, a ferromagnetic state
at very low electron density and a spin-liquid state with a spin pseudo-gap at
higher densities. (4) The metallic side of the transition is a non-Fermi
liquid. These conclusions are encapsulated in Figure 1 which presents the
proposed phase diagram as a function of disorder strength and density; we also
suggest experimental signatures of the various phases and transitions.
