This book introduces a powerful new framework for describing the states and dynamics of heterophase solids subjected to inhomogeneous stress fields. It serves both as an accessible introduction to the underlying theory and as a specialized monograph that deepens understanding of crack and dislocation behavior related to phase transformation. It addresses the interaction between such transformations and defects?primarily cracks and dislocations?though the approach is applicable to other, as yet unstudied, defect types. It further examines the effects of the stress-induced transitions on the mesoscopic properties of the material such as the peculiarities of the crack or dislocation motion, configuration of dislocations and elements of the dislocation ensemble. Finally, it studies variations of some macroscopic solid?s properties, such as the transformation toughness, shift of the elastic point, anomalous plasticity. All these aspects the book analyzes in relation to the solid?s position in the phase diagram. The authors? analysis combines computer simulations with analytical methods. The presentation is clear and self-contained, with all necessary derivations included, making it unnecessary for the reader to consult additional literature. The material is accessible to readers with a mathematical background equivalent to that of a third-year university student or higher. The book is intended for experimentalists, theorists, and students across disciplines interested in solid-state transformations and defect mechanics.