• Fluorescence is a non-destructive, non-invasive, intrinsic, and highly sensitive tool for monitoring various processes in biology and medicine.
• Stimulation of acceptor fluorescence and quenching of donor fluorescence is used to monitor excitation energy migration and transfer.
• Fluorescence is a highly sensitive, selective, and rapid analytical probe for measuring concentrations of very dilute fluorophores.
• Fluorescence can monitor the microenvironment of fluorescent molecules. Measurements of fluorescence include: (a) lifetime (information on the dynamics of biological processes); (b) quantum yield (information on photochemistry; heat loss); (c) polarization (information on organization) ; (d) action spectra ( information on excitation energy transfer); and (e) emission spectra

(nature of fluorophores), etc.
• Fluorescence spectrum is a mirror image of absorption spectrum, but shifted to longer wavelengths

(the Stokes shift)

• George G. Guilbault (1973) Practical Fluorescence, Theory, Methods and Techniques. Marcel Dekker, Inc., New York.
• David M. Jameson (1984) Fluorescence Principles, Methodologies and Applications. In Fluorescein Hapten: An Immunological Probe. E.W. Voss Jr.(Editor) CRC Press, pp. 23-48.
• Joseph R. Lakowicz (1983) Principles of Fluorescence Spectroscopy. Plenum Press, New York.
• Govindjee, J. Amesz, and D.C. Fork (editors) (1986) Light Emission by Plants and Bacteria. Academic Press, New York.

2.Historical

• "Luminescence" was first observed by Monardes in 1565 from the extract of Lignum Nephritcum, (that had been recommended for curing kidney ailments). However, Althanius Kircher (1646) was the first one to discuss, at length, its bichromatic appearance. It was yellow in transmitted light and blue in reflected light; the blue light must have been its fluorescence.
• Sir David Brewster ( 1834), a Scottish preacher, noted the red emission from chlorophyll in 1833. While discussing his concept of the color of natural bodies, he remarked almost in passing "In making a strong beam of the sun's light pass through the green fluid, I was surprised to observe that its colour was a brilliant  red, complementary to the green. By making the ray pass through greater thickness in succession, it became first orange and then…." The green fluid in Brewster's experiment was an alcohol extract of Laurel leaves. It must have contained chlorophyll, the pigment of green leaves, as named by Pelletier and Caventou (1818). I consider it likely that this was not only the discovery of chlorophyll fluorescence, but also of the phenomenon of reabsorption of fluorescence in thick samples.
• The clearest discovery of the phenomenon of fluorescence was that by Sir John Herschel (1845) in a clear solution of quinine sulfate. He noted the "celestial" blue color of this solution, but, had unfortunately called it

epipolic dispersion.. The following year Brewster (1846) designated it as internal dispersion.. It was left to Sir G.G. Stokes (see below) to call it fluorescence.
• Professor G.G. Stokes (1852), Professor of Mathematics at Cambridge University, who is well known for his discovery that emission bands are shifted to wavelengths longer than the absorption bands (the Stokes shift), first used the term dispersive reflexion, but quickly added a footnote: "I confess that I do not like this term. I am almost inclined to coin a word, and call the appearance fluorescence, from fluor-spar, as the analogous term opalescence is derived from the name of a mineral."[ Latin fluo=to flow + spar= a rock).]Stokes is the first one to recognize this phenomenon as light emission. Askenasy (1867) has credited Stokes also for the discovery of both phycobilin and chlorophyll a fluorescence in fresh red algae.
• The term "Phosphorescence" dates back to the early 1500s and was so named after the Greek "light bearing".  In fact, the element phosphorus was named from the same Greek word in 1669, since it was found to produce a bright light in a dark room.
• http://cfs.umbi.umd.edu/jrl/weber.htm provides information on Professor Gregorio Weber, who pioneered Fluorescence as a tool of biological structure and function; this note on him was written by J.R. Lakowicz

References:

• Harvey, E.N. (1957) A History of Luminescence From the Earliest Times Until 1900. The American Philosophical Society, Philadelphia, PA.
• Govindjee (1995) Sixty-three Years Since Kautsky: Chlorophyll a Fluorescence. Aust J Plant Physiol 22: 131-160.