This chapter consists of a survey of several common nanomaterials and their applications, combined with the fundamental physics required to understand the function of those materials, including transfer of energy and/or charge between components of a device. Nanoassemblies consist of many components held together by a series of specific interactions, whether covalent or noncovalent. Functional nanoassemblies, which are capable of responding to the presence of a target compound or energy source and responding to it by changing their own structure or performing work on their surroundings, are common in nature. Band theory is the generalization of molecular orbitals to larger systems. While often used in the context of bulk inorganic solids, it is also useful for understanding the electronic structure of large molecules and of nanomaterials. Charge transfer is the movement of an electron from one molecule to another or one portion of a molecule to another.