2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/29153We review recent experiments that provide evidence for a transition to a conducting phase in two dimensions at very low electron densities. The nature of this phase is not understood, and is currently the focus of intense theoretical and experimental attention.To appear as a Perspective in the Proceedings of the National Academy of Sciences. Reference to Chakravarty, Kivelson, Nayak, and Voelker's paper added (Phil. Mag., in press)Strongly Correlated Electronstext