Near-field Scanning Optical Microscopy (NSOM) is a high-resolution imaging technique that allows scientists to observe materials at the nanoscale. It works by using a sharp probe that scans very close to the sample surface, capturing light emitted from the sample. This method overcomes the diffraction limit of conventional optical microscopy, enabling the visualization of structures smaller than the wavelength of light. NSOM combines aspects of scanning tunneling microscopy and optical microscopy, making it valuable in fields like materials science and biotechnology. By providing detailed information about the optical properties of materials, NSOM aids in the study of nanostructures and their interactions.