Fluorescence is a special form of luminescence, an optical phenomenon in cold bodies, in which a molecule absorbs a high-energy photon, and reemits this light at a lower-energy or longer-wavelength.

Ultraviolet (UV) radiation is commonly used to excite fluorescence because it has enough energy to "kick" electrons to higher energy levels within a substance, which then results in the emission of visible light.

Sir George Stokes is credited with discovering fluorescence in 1852. Stokes' work laid the foundation for understanding this optical phenomenon.

Fluorescence has proven to be a versatile tool for myriads of applications. This powerful technique can be used to study molecular interactions in analytical chemistry, biochemistry, cell biology, physiology, nephrology, cardiology, photochemistry, and environmental science as well as in other areas.

The unit of measurement for the brightness or intensity of fluorescence is "lumens." Lumens measure the total quantity of visible light emitted by the fluorescent material.

Fluorescent dyes or markers are used in fluorescence microscopy to label specific structures or molecules within a sample. This labeling makes it possible to visualize and study these components under a microscope.

Fluorescence is not a universal phenomenon; it depends on the specific properties and composition of the material. Not all substances exhibit fluorescence when exposed to light.