Understanding the microscopic physics of deformation is critical in many branches of solid Earth science. Long-term geological processes such as plate tectonics and mantle convection involve plastic deformation of Earth materials, and hence understanding the plastic properties of Earth materials is key to the study of these geological processes. Interpretation of seismological observations such as tomographic images or seismic anisotropy requires knowledge of elastic, anelastic properties of Earth materials and the processes of plastic deformation that cause anisotropic structures. Therefore there is an obvious need for understanding a range of deformation-related properties of Earth materials in solid Earth science. However, learning about deformation-related properties is challenging because deformation in various geological processes involves a variety of microscopic processes. Owing to the presence of multiple deformation mechanisms, the results obtained under some conditions may not necessarily be applicable to a geological problem that involves deformation under different conditions. Therefore in order to conduct experimental or theoretical research on deformation, one needs to have a broad knowledge of various mechanisms to define conditions under which a study is to be conducted. Similarly, when one attempts to use results of experimental or theoretical studies to understand a geological problem, one needs to evaluate the validity of applying particular results to a given geological problem. However, there was no single book available in which a broad range of the physics of deformation of materials was treated in a systematic manner that would be useful for a student (or a scientist) in solid Earth science.