Thirty years of 2D MIT
The zero-magnetic-field metal-insulator transition in strongly correlated two-dimensional electron systems was experimentally discovered three decades ago, thereby triggering extensive experimental and theoretical investigations. Prior to this discovery, the occurrence of such a transition --- as well as the very existence of a metallic phase in two dimensions --- was regarded as forbidden within the framework of the one-parameter scaling theory of localization. In this work, we provide a comprehensive review of the transport and thermodynamic properties of two-dimensional electron and hole systems in which carrier-carrier interactions constitute the dominant energy scale. We present and critically analyze both experimental observations and theoretical developments accumulated over the past thirty years.