We present the results of computational simulation of dynamical processes of generation of equilibrium structures of electro-sensitive and magneto-sensitive mediums (electro-rheological fluids (ERhFs) and magneto-rheological fluids (MRhFs)). These fluids belong to the class of material with controllable properties. Materials with controllable properties are determined by characteristics of structures formed under the action of electric fields (ERhFs) and magnetic fields (MRhFs). We consider a three-dimensional unordered many-particle medium, namely, a suspension of dielectric particles (TiO2, CaCO3) (ERhF) or magneto-sensitive (ferrite) particles (MRhF) in a viscous medium. An initial configuration of particles of a representative volume of a medium is taken by chance. We describe the structure of ERhFs and MRhFs on the basis of direct computational experiments using the Monte-Carlo method in collaboration with the Metropolis procedure. We present the description of three-dimensional structures of the mediums under consideration under the action of electric and magnetic fields with the intensity varying over a wide range (from low field to high field). We determine the specific features of structural configurations of ERhFs and MRhFs corresponding to various values of concentration of the disperse phase as functions of strength of fields applied.