Because light is a wave, it has a wavelength, and a diffraction limit. (For details, see "Why does my bathroom light appear dim?") Because of the diffraction limit, materials smaller than the light's wavelength cannot be observed with a microscope using ordinary optical lenses. However, in the field of nanotechnology, needs exist to observe nanometer-sized or even smaller materials, and special microscopes employing a near-field light source are used. Diverse research is being conducted on this special light, which is beginning to find further applications outside microscopy.