The present chapter offers a valuable and quick insight into the fundamentals and applications of the Discrete Element Method (DEM) in chemical and process engineering. DEM is a computational technique by which the mechanistic collective behaviour of discrete entities (particles) during various processes are modelled. Unique capabilities of the DEM in predicting the particles' dynamics and interaction behaviour using a highly deterministic approach have made it a popular and essential computational technique in chemical engineers' toolbox. The principles of this method, including the governing equations, particle contact models, and particle shape representation techniques, are described in this chapter. In addition, the most famous commercial and open-source DEM codes are introduced briefly and an introduction to the EDEM commercial software, its main features, and the procedure for the simulation set up of a simple case-study are provided. In the end, some of the main applications of the DEM in the chemical and process engineering, namely packing, flow and mixing/segregation of particulate solids, as well as particle-fluid flow, are reviewed.