With rapid developments of nanosciences and nanotechnologies, there exists increasing demands for controlling structural, electrical, and optical properties of various organic and inorganic nanomaterials. As a post-synthetic treatment, this book introduces a new method for tuning and enhancing physical properties of organic nanomaterials with pi-conjugated structure through electron(E)-beam irradiation. Interactions between E-beam and pi-conjugated doped systems generate dedoping effects as well as conformational changes, which influence their energy band structures and corresponding electrical and optical characteristics. In addition to quantitative control with respect to E-beam irradiating conditions, not only simultaneous treatment of many nanomaterials but also nanoscale modifications within single strand are possible depending on type of E-beam (i.e., unfocused or focused ones).