Sizes of electronic and photonic devices are decreasing drastically in order to increase the degree of integration for large-capacity and ultrahigh speed signal transmission and information processing. This miniaturization must be rapidly progressed from now onward. For this progress, the sizes of materials for composing these devices will be also decreased to several nanometers. If such a nanometer-sized material is combined with the photons and/or some other fields, it can exhibit specific characters, which are considerably different from those ofbulky macroscopic systems. This combined system has been called as a mesoscopic system. The first purpose of this book is to study the physics of the mesoscopic system. For this study, it is essential to diagnose the characteristics of miniaturized devices and materials with the spatial resolution as high as several nanometers or even higher. Therefore, novel methods, e.g., scanning probe microscopy, should be developed for such the high-resolution diagnostics. The second purpose of this book is to explore the possibility of developing new methods for these diagnostics by utilizing local interaction between materials and electron, photon, atomic force, and so on. Conformation and structure of the materials of the mesoscopic system can be modified by enhancing the local interaction between the materials and electromagnetic field. This modification can suggest the possibility of novel nano-fabrication methods. The third purpose of this book is to explore the methods for such nano-fabrication.