It is often a challenge to measure accurately the mechanical properties of nanostructures and nanomaterials on account of their extremely small physical dimensions. Recently, Hysitron have developed an in situ TEM nanomechanical testing apparatus which enables one to acquire quantitative mechanical data while simultaneously recording the microstructure evolution of the materials during deformation, developing a one-to-one relationship between imposed stress and individual deformation event. In this talk, I will report our recent progress in the application of this in situ TEM device for measuring the mechanical behavior of individual nanostructures.