abstract: The main objective of the authors of that book was to present the current state of study of mechanical properties of granular solids with special focus on agro and food biologically based granular materials. The main features of biologically based materials that make them different from mineral materials are: strong influence of moisture content on mechanical behavior and high deformability of granules. These differences bring about certain peculiar behaviors and enforce adjustments of contact models and calculation techniques. This work review currently available solutions and present problems that have a chance to be solved in the nearest future. Out of these only narrow portions of knowledge were presented in this book that are directly tight with the phenomena encountered by the authors in their laboratory examinations or in practice. The main theoretical approaches - continuum and discrete ones were presented in that book. The continuum theory that consider a volume of material as a solid body or a liquid, was the earliest approach of scientists for predicting behaviors of bulk solids. Continuum approach led to solutions of numerous problems of technology but it failed in the cases where interactions between grains were important. Thus, the opposite option is to model every single grain using discrete approach. The computational technique which allows tracking the motion of each individual particle and obtaining detailed information about the system behavior is the Discrete (or Distinct) Element Method (DEM). For simulations, the trajectory and rotation of each particle in a system are obtained using a numerical time integration scheme. Today simulations of several thousands of 3D spheres or ellipsoids are conducted. Still long way remains to come regarding that the mass of 1000 seeds of wheat is approximately 40 g, thus 40 kg sack contains approximately one million kernels. Success of DEM examination of granular material rely on proper use of concepts from several branches of science and engineering, such as: mechanics of continuum, impact mechanics, contact mechanics, strength of materials and programming. The presented work contains brief description of the most popular theoretical approaches, presents popular methods and equipment for determination of material parameters and interesting results of discrete element modeling of behavior of granular plant materials.