Theoretical and computational research on materials play a central and steadily growing role in both materials science and chemical engineering. The most important roles of theory are to provide a conceptual paradigm for understanding material properties, and to sharpen the questions that we ask about experimental data. Computational studies often also play a crucial role in guiding the interpretation of specific experiments, and are increasingly able to guide the design and selection of materials for applications. Researchers in CEMS uses a variety of approaches to describe different types of materials and phenomena over a wide range of length scales. Approaches pursued here include ab initio quantum mechanical studies of electronic properties and equilibrium structures, studies of coarse-grained models of polymers and other soft materials, and continuum-level studies of materials processing.