Recent progress in near-field optics instrumentation has led to a new class of subwavelength optical experiments in which near-field optical microscopes are used to image precisely the electromagnetic field distributions inside nanostructures microfabricated at the surface of dielectric wafers (microwaveguides, optical splitters, whispering-gallery modes, three-dimensional photonic crystals, metal nanoparticle gratings, plasmon waveguides, etc). In the light of these new advances, we review the physics of near-field optics in the presence of nanostructured materials (the so-called nano-optics). After the introductory part, revealing the main theoretical schemes and computation techniques well-suited for nano-optics, we will focus on several typical examples of calculations extracted from the recent literature. We will begin this series by revisiting the challenging problem of the optical addressing of both passive or active nanostructures in a subwavelength area. In this context, various procedures for the optimization of the energy transfer efficiency inside addressed nanostructures will be detailed. Finally, the concept of photonic local density of states in near-field optics will be revisited.