Book excerpt: Optics of Excitons in Confined Systems provides an overview of research in semiconductors that exhibit resonance enhanced optical nonlinearities in the frequency range close to the valence-conduction band gap. The book is divided into the following sections: quantum wells, wires, and dots; superlattices; nonlinear optical properties of confined systems; and effects of external fields on confined systems. Topics range from fundamental theory to more applied aspects of excitons in confined sytems.