The problem of superconductors has been a central issue in Solid State Physics since 1987. After the discovery of superconductivity (HTSC) in doped perovskites, it was realized that the HTSC appears in an unknown complex electronic phase of c- densed matter. In the early years, all theories of HTSC were focused on the physics of a homogeneous 2D metal with large electron electron correlations or on a 2D polaron gas. Only after 1990, a novel paradigm started to grow where this 2D metallic phase is described as an inhomogeneous metal. This was the outcome of several experimental evidences of...