The development of faster and smaller electronic devices leads from microelectronics to nanoelectronics. In nanoscopic or mesoscopic systems quantum effects such as the quantum Hall effect, new electronic transport phenomena and other aspects of electron-photon interactions become important. The physics of mesoscopic systems, the relevant effects and phenomena and new quantum device concepts as well as the formation and characterization of quantum structures are discussed. This is the most comprehensive presentation of the basis and realization of a new and promising concept for future electronic devices. This book is a must for all researchers in this field.