Pineal gland is a good place to start. It's located at the center of the brain, taking up a little space. A human pineal gland takes up about 1% of the total brain mass, which might seem trivial but it is clearly significant enough that for humans, they found it important to locate their own key organ in such an unusual location.
A pineal gland is very distinct from other organs in the body. The key function of a pineal gland is that it produces melatonin - an endocrine hormone that regulates sleep and wake cycles, circadian rhythms, seasonal breeding patterns etc.
Interestingly, the pineal gland is not a necessary organ in humans. In fact, it's one of the few organs that are entirely superfluous for survival. Most animals have a pineal gland but it has evolved into different forms in each group
It's in the pineal gland that the awakened people can get information about themselves and others. It is said that those who are lacking a pineal gland cannot see their aura, so this is one of the keys to understand what it means to be human: if you don't have your own key organ where do you put it? The answer would be - nowhere.
Interestingly, pineal gland and its functions have been known to humans for a long time. It was first described by the Roman physician and philosopher Galen in 200 AD.
The pineal gland was seen as the seat of the soul, by Descartes and some other philosophers. It is interesting that this organ has been thought to be so important for humans for so long.
The pineal gland is a small endocrine gland in the vertebrate brain. It produces and secretes the hormone melatonin, a derivative of tryptophan and serotonin among others. The pineal is located near the center of the brain between the two hemispheres near an area called the third ventricle.
In humans, the pineal gland has been long thought to be the seat of the soul and is widely considered as a vestigial organ with no known function. It contains cells that make melatonin which are light sensitive. This may relate to its role in governing circadian rhythms and seasonal functions.
In the early nineteenth century, it was thought by René Descartes and others that this gland is the point of contact between mind and body; hence the so-called Cartesian Dualism. Some have even suggested that in humans it secretes DMT.
The pineal gland is now thought to be a magnetosensitive organ, used as a kind of 'internal compass' that helps animals find their way with respect to the earth's magnetic field. This may help birds and sea mammals navigate across great distances.
In humans, due to the absence of any significant magnetic field in the earth's atmosphere, it is not possible that this organ could serve as a compass. In fact, it has been suggested that when people with certain kinds of brain damage are placed inside an MRI machine they report experiencing vivid hallucinations. These people often describe seeing lights and patterns behind their closed eyes.
Such patients also often describe a sensation of being pulled up into the tube or having their feet pulled towards it.
The pineal gland is an endocrine gland in the vertebrate brain. It produces melatonin, a hormone that affects the modulation of wake/sleep patterns and photoperiodic (seasonal) functions.
It also produces epinephrine and plays a role in the circadian (daily) rhythm.
As the eye of the soul, it is hard to describe. It's like a lens that perceives internal and external reality. The pineal gland illuminates what we call intuition.
It feels like a truth detector. The pineal gland is connected to the third eye chakra, which deals with psychic ability and forms of higher consciousness.
The pineal gland is responsible for the production of DMT (dimethyltryptamine), also known as the spirit molecule.
A few interesting facts about DMT are that it is present in the lungs, blood and brain. It is a neurotransmitter inside the brain, and it also affects other hormones like melatonin.
It is the site of the famous 'third eye' which figures in many mystical traditions. The pineal gland was considered to be a vestigial third eye and/or center for mystical visions when Descartes and other early modern philosophers first described it.
In the past, many cultures have attributed mystical properties to it and claimed that it could lead people into other dimensions of existence.
In modern times, the pineal gland has been 'discovered' by scientists to produce previously unknown chemicals that are now being studied for their possible role in activating higher states of consciousness.
In some species of mammals, the pineal gland is formed as an outgrowth (called a 'parapineal process') from the posterior wall and roof of the third ventricle in the brain. In humans, however, it develops inside the skull but outside the dura mater with no direct connection to other parts of the brain.