The book emphasizes the role of surface effects in optical phenomena in nanoscience from two different perspectives. When systems are reduced in volume, the surface versus volume ratio increases: this translates, at the level of single nanostructures, into enhanced role of interfacial chemistry and thermodynamics, and, at the level of systems of nanostructures, into larger density on interfaces, which in turn leads to intriguing collective effects, such as plasmonics or multiple reflection and refraction phenomena. The book aims to highlight both perspectives presenting sample applications, with no claim of being exhaustive, but rather attempting to stimulate the reader in this potentially rewarding field.