Much has been written and speculated about this small gland whose function remains only partially understood.
The philospher Rene Descartes called it 'The Seat of the Soul' and proposed that it had a mind-body unifying function, integrating the tangible aspect of corporeality and sense pereception with the intangible qualities of thinking and imagination.
Its acknowledged role as a gland in the hormonal system is to produce Melatonin, used to regulate our sleeping patterns, and Serotonin, which makes us feel good.
Recently it has also been found to produce DMT ( DiMethylytryptine) which has been shown to produce enhanced states of conciousness and inner visions, which e connects to its historical status as the organ of the Third Eye : the means by which human beings can have access to interior visions and perceptions of reality which transcend the material, a property almost universally ascribed to human beings in the pre-modern area .
Evidence has emerged to provide physiological support for this understanding, for, although located almost in perfect center of the Cranium and far from any entering light stimulus, researchers have found that the hollow, water filled gland contains photoreceptor rods and cones similar to those found in our retinas ( report in Neurochemical Journal ), and even Calcite crystals ( report here on Research Gate ).
Calcite is a a translucent to transaprent crystal which has the optical properties of birefringence ( splitting light path to produce two images of an object) and Luminescence, light emission.