The motion of electrons in mesoscopic systems such as Aharonov-Bohm rings, small Josephson and tunnel junctions, quantum wires dots, and point contracts is presented in this volume in terms of a fully quantum mechanicaldescription of electronic states and current flows in solids. The comprehensive reviews by leading scientists in the field on the present understanding of mesoscopic systems will serve as a good basis for further development of the science and technology of quantum devices.