The aim of this volume is to provide an overview on the state-of-art in optical spectroscopy covering the focal theoretical and experimental aspects of the last research developments on semiconductor field. Some key topics in semiconductor science, namely: optical spectroscopy as a tool for in situ epitaxial growth monitoring and non-destructive surface and interface characterizations in mesocopic superstructures are addressed in the book. A non-exhaustive list of arguments is: surface and interface characterization, chemical reactions in semiconductor surfaces, heterostructures, quantum wells and superlattices, nanostructures and microlasers.