A photon is a quantum of light, or the smallest possible packet of light at a given wavelength. It is emitted by an atom during a transition from one energy state to another. Photons travel at the speed of light and have mass and momentum dependent on their frequencies. By classical reasoning a photon would have the apparent dualistic property of being either a particle or a wave disturbance. Light is electromagnetic radiation in the wavelength range extending from about 0.4 micron to about 0.7 micron. Two sinusoidal oscillations of the same frequency are said to be mutually coherent if they exhibit a constant phase relationship during the course of time. For example, a laser is coherent and sunlight is partially coherent.

It is now well established that all living systems emit a weak light current of some photons. The discovery was made in 1920s by Alexander Gurwitsch, a Russian biologist, who called this photon emission from living cells “mitogenetic radiation,” in order to express its growth stimulating capacity. The intensity of this ultra weak light is nearly equal to intensively of light of a candle placed at a distance of 10 Km. Photo electric devices to measure this weak light were developed in 1950s. Scientists found that the nature of this, weak light emitted by living cells is different from the sunlight. They called these light photons as bio-photons.

The pioneering work done by Fritz � Albert Popp has given a deep insight into the phenomenon of bio photon emission. According to him the purely molecular aspect of life sciences may be only one necessary step in understanding biology and can never reach the significance of sufficient and complete explanation. Molecules have no intelligence, despite the manifold impressive functions that have been assigned to them. Even the enzymes or messenger molecules have to be triggered by external energy, i.e. photons which activate the diversion transition state complexes. These activation energies cover the whole electromagnetic spectrum. The non-thermal photons provide the right quantum energies at the right place and right time for the millions of reactions per second per cell. Thus, one has to stress that (1) It is impossible that thermal photons may trigger the biochemical reactions in a living system, and (2) that theoretically only one photon per cell could be sufficient for activating 109 reactions per second, provided that it originates from a coherent photon field. If this field is coherent and non-thermal one, it is theoretically able to borrow the photon energy at the right time and take it to the right position of the reaction and to reabsorb it immediately after this event which, in general, takes not longer than about 10-9 seconds.

Consequently, the weak photon current from biological systems, which � as we know nowadays covers the whole spectrum range at least from UV to infrared and which we call “bio photons” may well suffice to take the role of regulating the whole biochemistry and biology of life. The bio photon emission displays a few up to some hundred photons per second per centimeter square within the spectral range from at least 260 to 800 nm. It is closely linked to delayed luminescence of biological tissues which describes the long term and ultra weak reemission of photons after exposure to light illumination.

What are the consequences of coherence? It results in properties that are characteristic of biological systems. These include the high efficiency of energy transfer and transformation which often approaches 100%; the ability of communication at all levels within cells, between cells and between organisms capable of resonating to the same frequencies; the possibility for sensitive, multiple recognition systems utilizing coherent electromagnetic signals of different specific frequencies, such as for example, the organization of metabolic activities within the cell, the operation of the immune network and a host of other biological functions involving specific recognition between hormones or ligands and their receptors; and finally, the stable persistence of the working system arising from the inherent stability of coherent states.

Practically all organisms emit light at a steady rate. An increasing number of observations from different laboratories all over the world suggest that bio photons are emitted from a coherent photon field within the living system. Organisms are thus emitters and most probably, also receiver of coherent electromagnetic signals which may be essential for their functioning. When the spectrum of bio photons is examined, it was found that the light is always in a broad band of frequencies from the infra-red to the ultraviolet, with approximately equal number of photons distributed throughout the range. In other words the distributions does not depend on the wavelength; f( ) = const. This means that the light is emitted from all kinds of molecules all over the cell. The living systems store energy (or photon) from 10-10 m to meters or more, and 10-9 second to days or longer time intervals � in a readily mobilized form. They do not suffer from energy shortage on account of their high storage capacity within the intricate space-time organization.

Systematic measurement of bio photon emission of the human body has shown the following results. (1) The left right symmetry of the human � body, (2) biological rhythms such as 14 days, 1 month, 3 months and 9 months; (3) disease in terms of broken symmetry between left and right side, and (4) light channels in the body, which regulate energy and information transfer between different parts.

The bio photon emission is indicative of an endogenous, innate, electromagnetic field pervading the entire organism, which may act as both sender and receiver of the bio photon that are “electromagnetic bio � information” used in regulating life processes. These observations, among others, suggest control within the living state that is non-local and possibly electromagnetic in nature. Many significant correlations between features of the weak biological light and a number of fundamental biological processes, such as cell division, death, and major shifts in metabolism, exist. These correlations may indicate that the light (electromagnetic field of the organism) is a sensitive, global expression of biological regulating processes.

The bio photon is trapped and remitted by DNA, which undergoes physical resonance, resulting in light emission with at least some coherence. Biological process may be integrated by the endogenous bio electromagnetic field that has a primary organizational and informational role. Conformational states of DNA may serve as the photon storage of the coherent modes of the electromagnetic field within the cell.

From the bio physical point of view bio photons are regulating the body in its rather complex functions. The interference patterns of bio photons originating from the resonance tuning between the coherent field and biologically matter (preferentially DNA) governs the availability of energy in a concerted action of the whole. Consequently, the organizational capacity is reflected by characteristics of bio photon emission.

The biological and physical activities affecting bio photons signals belong to the macroscopic class. The sensitivity is such that a bio photon signal appears to provide faithful reflections of biological and physiological activities of the emitting system. If it is true for all macroscopic biological activities, then a bio photon contains decipherable and digitized signature of all macroscopic biological activities. Bio photon emission is thus seen a crucial evidence of a physical basis of life.