Brightfield microscopy is the simplest of all the optical microscopy illumination techniques. Sample illumination is transmitted (i.e., illuminated from below and observed from above) white light and contrast in the sample is caused by absorbance of some of the transmitted light in dense areas of the sample. llumination is not altered by devices that alter the properties of light (such as polarizers or filters). In biological applications, brightfield observation is widely used for stained or naturally pigmented or highly contrasted specimens mounted on a glass microscope slide. This technique is widely used in pathology to view fixed tissue sections or cell films / smears. Brightfield imaging is not very useful for unstained living cells or unstained tissue sections as, in most cases, the light passes through transparent or translucent samples with little or no definition of structure.