Abstract: Z－contrast scanning transmission electron microscopy (Z－STEM) can directly provide imaging at an atomic resolution. With the help of aberration correction, a resolution as high as 0.6 can be reached. In this article we will describe some typical applications of Z－contrast STEM imaging. From the cathodoluminescent properties of Eu doped Y2O3 thin films, we reveal the presence of the "dead layer". Then, with three examples, we present the unparalleled advantages of Z－contrast imaging in determining the structure, physical properties and chemical composition of crystals.