The direction of our research is to investigate the uniformity of active sites in single atom catalyst and how they affect the activity of the catalytic process. The uniformity of activity site of single atom catalyst will be different due to various synthetic method, reaction condition and raw material?™s composition. The difference in uniformity can change the coordination structure and electronic configuration of the SAC which will modulate the absorption behavior and affect the reactivity of catalytic reaction. XAS is important technique to characterize the uniformity of active site by using EXAFS and XANES spectrum. To characterize the coordination structure, EXAFS mode can be used. In this mode, the X-ray is absorbed by the selected atom, and core electron of selected atom will be excited and scattered by neighbor atom. It can be used to find the interatomic distance after fitting the experimental data with theoretical model. XANES can be used for characterize the electronic configuration of SAC. It is able to reflect the oxidation state and electron structure of the measure atom by studying the edge energy position and the shape of XANES spectrum. Operando XAS technique is also useful for this research. Not only monitoring the structure and chemical state of the SAC, it can also be used to study the catalytic reaction mechanism under the reactive atmosphere. This technique can provide more information about the catalytic process. Based on the importance of XAS, I believe that joining this summer course will gain a lot of help on our research and future study.