Fluorescence microscopy is based on the principle of removal of incident illumination by selective absorption, whereas light that has been absorbed by the specimen and re-emitted at an altered wavelength is transmitted. The light source must produce a light beam of appropriate wavelength. An excitation filter removes wavelengths that are not effective in exciting the fluorochrome used. The light fluoresced by the specimen is transmitted through a filter that removes the incident wavelength from the beam of light. As a result, only light that has been produced by specimen fluorescence contributes to the intensity of the image being viewed.


Acridine orange
Rhodamine — auramine
Calcofluor white
Fluorescein isothiocyanate
Lissamine rhodamine


1. For fluorochrome staining of tissues, cells or bacteria by using dyes like acridine orange, auramine O, calcofluor white, etc.

2. For immunofluorescence by using fluorescent dyes like fluorescein isothiocyanate & lissamine rhodamine to label the antibodies or antigens.​​