The discovery of superconductivity behaviour in ceramic materials based on copper oxide suggests that ceramic can be used as an insulator material. However, superconductivity mechanism-based copper oxides are still seen as mysterious and misunderstood by scientists, even though the search for materials with higher critical temperatures has been ongoing. This effort can be seen from the first discovery of superconductor in the critical temperature of mercury 4.2 K up to the highest critical temperature of 164 K in the copper oxide superconductors Hg-Ba-Ca-Cu-O in 1993. This book discusses the development of high temperature superconductors since the discovery of the first superconductor until now, as well as the basic properties of high temperature superconductor. In addition, it also describes various wet chemical methods in superconductors preparation.