Only the remainder of light unharvested by plans penetrate to those depths. To date, more than three hundred photochemically reactive proteins, capable of harvesting low light energy, have been identified in both prokaryotic and eukaryotic organisms. Many more are being discovered yearly. In humans, the most commonly known photochemically active receptor proteins are rod and cone pigments in the eye. However, other human photoreceptors have been discovered in recent times.
Examples are encephalopsins in the brain, and pinopsin in the pineal gland.
Given the discovery of photoreceptor proteins in the pineal gland, the hypothalamus, and other tissues of lower vertebrates, it is only a matter of time that it will become clear that other human tissues have photoreactive proteins as well. Moreover, there are clearly defined human ocular and extraocular metabolic processes that depend on small packets of light harvested by known chromophores. The challenges faced by researchers in this field are to clearly identify those chromophores that are triggered by low power laser, to determine the photochemistry of the chromophores, and to demonstrate how their responses to laser light produce beneficial clinical changes. In this regard, reports which indicate that chromophores in human mitochondria can be activated by laser light to initiate photochemical processes that elevate ATP and protein synthesis, are encouraging. They are consistent with the photochemical reactions of other chromophores, and should be replicated to elucidate how such light-induced quantum changes produce clinical benefits.