Conventional optics is diffraction limited to about half of the effective optical wavelength. However the current trend
towards miniaturization of optical elements and devices requires methods of observation with high spatial resolutions
adapted to the micrometer and submicrometer optical regime. More specifically, the use of Scanning near-field optical
microscope (SNOM or NSOM) in various domains is overviewed. Basically an optical tip with a subwavelength
aperture at its apex scans over a surface with a spatial resolution, which is not limited by light diffraction. This
characteristic makes SNOM a valuable tool to perform various optical or spectroscopic studies on nanoobjects, such as
semiconductor quantum dots (QDs), or to address them optically. The paper reviews different methods of far-field and
near-field approach to visualize nano-size objects.