Electrons traveling along the direction that has been reduced in size reach the boundaries, that is, the surfaces of the specimen, and are con ned in nanospace. This con nement causes the quantization of the electron wavelength and the energy spectrum. In addition, the cyclic boundary condition is broken at the edges (surfaces), and the contribution of the edge-localized electronic states (surface states) dominates the total electronic structure. The electron-charging energy also increases dramatically due to the size-dependent increase in the electrostatic capacitance of nanoscale materials. Furthermore, reduction in the size leads to the manifestation of electron tunneling phenomena.