The use of a combined thermodynamic and diffusion kinetic approach in predicting the product morphology developed during solid-state displacement reactions is exemplified by the interactions in the GaSb/Co and SiC/Me (where Me=Cr,Pt,Co) systems. The influence of mechanical stresses induced during the interaction on the formation of microstructures is demonstrated. It was shown that the manifestation of the effects accompanying reactive-phase formation in inorganic solids (like the Kirkendall effect and the net volume change during internal precipitation) causes the generation and relaxation of the stresses. This significantly contributes to the morphological evolution of the reaction zone. Different micro- and macrodefects (vacancies, dislocations, pores, cracks, etc.) that can be generated inside the diffusion zone can also affect (or even control) the course of the reaction and determine the topological arrangement of the product phases within the resulting microstructure.