internal stresses that arise in crystals in the absence of external forces and are equilibrated within volumes that are small compared to that of the entire body. They are caused by imperfections of the crystal structure, such as point defects and clusters of them, and also dislocations. With decreasing distance from a defect, the stresses in the crystal increase and may reach values of the order of the ultimate strength of the material. Microstresses determine a number of the physical properties of crystals, above all the mechanism of their plastic deformation and failure.