The search for microscopic models to explain the many superconducting substances has introduced seminal concepts and techniques in many-body physics and in statistical mechanics. The complexity of the high-temperature superconductors has required a remarkable refinement of experimental techniques in order to allow a reliable characterization of the samples, and is partly the reason why so many different microscopic models have so far been proposed. This Enrico Fermi Course on Superconductivity was provided an up-to date presentation of selected experimental and theoretical theories on the (so.