This unique book provides a concise and systematic treatment of foundational material on dislocations and metallurgy and an up-to-date discussion of multiscale modeling of materials, which ultimately leads to the field theory of multiscale plasticity (FTMP). Unlike conventional continuum models, this approach addresses the evolving inhomogeneities induced by deformation, typically as dislocation substructures like dislocation cells, as well as their interplay at more than one scale. This is an impressively visual text with many and varied examples and viewgraphs. In particular, the book presents a feasible constitutive model applicable to crystal plasticity-based finite element method (FEM) simulations. It will be an invaluable resource, accessible to undergraduate and graduate students as well as researchers in mechanical engineering, solid mechanics, applied physics, mathematics, materials science, and technology.