Staining in histology involves the use of dyes that absorb specific wavelengths of light. The absorption properties are dependent on the chemical structure of the dye and the wavelength of light used. For example, Hematoxylin absorbs light in the blue-violet range, making cell nuclei appear blue under a microscope. Conversely, Eosin absorbs light in the green range, staining cytoplasmic components pink.
