The electrical transport properties of solids are strongly affected by disorder caused by the presence of impurities or imperfections in the crystal lattice. In 1958, in an article titled “Absence of diffusion in certain random lattices,” P. W. Anderson demonstrated that disorder can spatially localize the electron charge carriers; that is, they become unable to carry an electric current because of their quantum-mechanical wave character. He simultaneously formulated the problem of electron localization in a disordered metal, made the link between localization and electrical transport, and gave the first quantitative estimate of the critical disorder for the disorder-driven metal-insulator transition.