Scanning Near-field Optical Microscopy (SNOM) is a powerful technique that scans a tapered optical fiber across the sample,illuminating only that area of the sample that lies directly under the tip aperture (~100nm). Kept within few nanometersof the surface, the tip illuminates the sample in the near field allowing the collection of optical information of the surface ofthe sample, with a resolution better than the diffraction limit of the operating light. In addition, this technique could be usedin order to perform spatial resolved photocurrent measurements on photovoltaic devices. The immergence of SNOM openedup fields of studies that were inaccessible. The basic principles behind the enhancement of the optical resolution by SNOM,especially the detection of the high spatial frequencies that are very confined in the near field regions, are going to be discussedduring this poster.