The probing and modeling of carrier transport in materials is a fundamental research subject in electronics and materials science. According to the Maxwell electromagnetic field theory, there are two kinds of currents, i.e., conduction current and Maxwell displacement current (MDC). The conduction current flows when electronic charges, e.g., electrons and holes, are conveyed in solids, whereas MDC is the transient current that is generated due to the change of electric flux density. The source of conductive current is charged particles, i.e., electrons, holes, ions, etc., and the source of MDC is also the charged particles. It is therefore anticipated that we can probe and model carrier transport in materials, in terms of 'MDC'. In other words, we can find a novel way for modeling and analyzing materials on the basis of Dielectric Physics Approach, on focusing dielectric polarization phenomena. Maxwell Displacement Current and Optical Second-Harmonic Generation are basically dielectric phenomena. The aim of this book is to show the dielectric physics approach for the study of molecular materials and organic electronics devices related to carrier transport and dielectric polarization, on focusing Maxwell Displacement Current and Optical Second-Harmonic Generation in Organic Materials from viewpoints of Analysis and Application for Organic Electronics.