The localization of electrons in a disordered solid that occurs because of that disorder. The localized states are at the tails of the energy bands, with critical energies called mobility edges separating these states from extended states, i.e. states that can propagate through the solid. Localized states cannot conduct electricity at absolute zero but extended states can. A mobility edge is analogous to a critical temperature in a phase transition. Indeed, Anderson localization can be analysed using methods used in the theory of phase transitions. In one dimension any amount of disorder results in Anderson localization for all states. In three dimensions there needs to be a critical amount of disorder before all states are localized. The concept of Anderson localization was proposed by the US physicist Philip Anderson (1923– ) in 1958.