The book "Optics of Semiconductors and Their Nanostructures" provides a comprehensive introduction to the optics of semiconductors and their nanostructures. In recent years, the field of semiconductor optics has rapidly evolved, with the dimensions of semiconductor structures shrinking to just a few nanometers. The interactions between semiconductors and light are studied on extremely short timescales of just a few femtoseconds. These advancements are the result of rapid developments in semiconductor and optics technology, as well as the theoretical description of optical excitations in semiconductors. Written by leading experts, the book covers both current developments and novel applications, including blue light-emitting devices and future applications in areas such as spintronics, quantum information processing, and third-generation solar cells.