One of the main motivations for studying superconductivity is to search for high temperature superconductors, especially, room temperature superconductors. During the long history of more than 100 years since the discovery of superconductivity, a number of high temperature superconductors were found and several great breakthroughs were achieved. Recently, thanks to advances in computing power, progress in crystal structure prediction, and developments in density functional theory, computations have been carried out to predict the structures and an appearance of superconductivity of hydrides at high pressure. More exciting, it is been the first time when a simple, perfect cubic phase of H3S which become superconductor at Tc=200 K under high pressure was successfully predicted by means of ab initio calculation, and then confirmed experimentally. This observation breaks the temperature record of cuprate with Tc= 164 K and further stimulates the studies of hydrides under pressure. Very recently, the high value of Tc = 286 K was theoretically predicted for LaH10 at 210 GPa and this prediction has been confirmed experimentally. These two successful examples demonstrate the importance of ab initio approach to superconductivity.