Destruction of superconductivity in granular and highly disordered metals

The destruction of superconductivity in granular and highly disordered metals is discussed in the light of the modern picture of the metal-insulator transition induced by Anderson localization. For small grains superconductivity is lost when localization sets in. Systems composed of large grains may phase lock at a temperature, $T_C$, much smaller than the $T_C^0$ of the clean metal. $T_C$ is estimated as a function of the appropriate parameters and the results are shown to be consistent with existing experiments.