Hybrid perovskite solar cells are exciting due to their solution-processability, defect tolerance, and high power conversion efficiency of 25.5%, comparable to commercial technologies. However, their instabilities and ion migration issues are bottlenecks limiting commercialization. Here, we start from studying materials formation process, designing preferential interfaces, investigating behavior under different stress factors, to stabilizing the performance of the solar cells. Our goals are not only to develop design criteria for stability but also be able to maximize the performance of the solar cells under realistic operating conditions.