Provides the theoretical background needed by physicists, engineers and students to simulate nano-devices, semiconductor quantum dots and molecular devices. It presents in a unified way the theoretical concepts, the more recent semi-empirical and ab initio methods, and their application to experiments. The topics include quantum confinement, dielectric and optical properties, non-radiative processes, defects and impurities, and quantum transport. This guidebook not only provides newcomers with an accessible overview (requiring only basic knowledge of quantum mechanics and solid-state physics) but also provides active researchers with practical simulation tools.