The advent of semiconductor structures whose characteristic dimensions are smaller than the mean free path of carriers has led to the development of novel devices and given rise to many advances in our theoretical understanding of these mesoscopic systems or nanostructures. This book reviews the results of experimental research into mesoscopic devices, and develops a detailed theoretical framework for understanding their behavior. The book will be of great interest to graduate students taking courses in mesoscopic physics or nanoelectronics, as well as to anyone working on semiconductor nanostructures or the development of new ultrasmall devices.