Since the first report on the solid-state perovskite solar cell with power conversion efficiency (PCE) of 9.7% and 500 h-stability in 2012 by our group, perovskite photovoltaics have received great attention. As a result, the highest PCE of 22.1% was reported in 2017. It is believed that perovskite solar cell is promising next-generation photovoltaics due to superb performance and very low cost. Although high photovoltaic performance was demonstrated, perovskite solar cell is suffering from current-voltage hysteresis. Since hysteric perovskite solar cell cannot guarantee long-term stability, development of methodology toward hysteresis-free perovskite solar cell is important. The hysteresis in perovskite solar cell is especially pronounced in normal mesoporous structure having TiO2 electron transfer layer. Inverted structure was proved to show non-hysteric behavior, which is however inferior to the normal structure in terms of PCE. Thus, it is important to explore effective ways to remove hysteresis in normal perovskite solar cell employing TiO2. In this talk, defect, both bulk and surface defects, is emphasized as origin of the hysteresis. Interfacial engineering is found to be one of effective methods to reduce hysteresis and improved improve stability simultaneously. However, interfacial engineering might not be sufficient to remove hysteresis completely. We successfully discovered a universal approach toward hysteresis-free perovskite solar cell, which will be discussed in detail.