Our main goal is to use computer modeling methods (e.g. tetrahedra, implicit surfaces, particle system) to obtain realistic models of internal human organs. However, our approach may be applied to any domain requiring physically-based modeling. As an application, we gather medical, physical and computing data to develop a personalized simulation of moving and deforming organs, with special interest on breathing simulation. Most often, the internal (organ deformation) or external (collision between organs) interactions are implemented using discrete or continuous laws. To perform realistic simulations, it is necessary to understand the relation between parameters of the potential and the physical physiological and/or biomechanical properties of the material under studies. This will permit as well to incorporate heterogeneity and anisotropy in the environment. Keywords: physically based modeling, soft organs, discrete modeling.