High temperature superconductors are materials that superconduct at unusually high temperatures. Common ingredients of these materials are cooper-oxides (cuprates) and antiferromagnetic insulating phase nearby superconducting state. Since the discovery of superconducting state in the cuprates in 1986, the transition temperature has been raised up to above 150 Kelvin (under pressure). The cuprates have not only generated intensive research on possible realization of room temperature superconductors, but also provided a playground to study the rich physics of strongly correlated systems. Innovative ideas including spin liquid and competing order parameters are by-products of cuprates studies, which are now widely used in understanding properties of other correlated materials. See our papers in arXiv.org for details. In particular, ” An explanation for a universality of transition temperatures in families of copper oxide superconductors”, published in Nature 428, 53 (2004).