Abstract: Recent progress in the application of in situ transmission electron microscopy (TEM) is briefly eviewed. It is emphasized that the development of advanced in situ TEM techniques makes it possible to investigate the volution of materials under heat, strain, magnetic field, electric field or chemical reaction nvironments on the atomic scale. The mechanism of the microstructure evolution under various conditions and the relationship between the atomic structures and their properties can be obtained, which is beneficial for the design of new materials with tailored properties. The clarification of the structure-property relationship will help to develop new materials and solve related basic problems in the field of condensed matter physics.