To date more than ten high temperature superconductors (HTSC) have been discovered, which are all oxides with perovskite related crystal structures. Starting from Tc=30K in La-Ba-Cu-O in 1986, Tc has risen every year along with the discovery of new materials. Y-Ba-Cu-O in 1987 was the first HTSC with Tc higher than the liquid nitrogen temperature and Tc exceeded 100K in 1988 by the discovery of Bi-Sr-Ca-Cu-O. These compounds are particularly important for technical applications. Although the rise of Tc seems to have taken a pause over a year, a representative HTSC has appeared also in 1989. This is Nd-Ce-Cu-O and the first N-type HTSC with electrons as charge carriers. From these discoveries it is now almost established that the two-dimensional CuO2 plane as well as doping carriers into it are essential for realizing high temperature superconductivity.