The pineal gland, in the region of the third eye, is a pea-sized endocrine gland. It has the physical purpose to produce melatonin, which regulates sleep patterns in the circadian and seasonal cycles. However, it is also considered to be a mystical part of the human body. Many cultures throughout history and even today view the pineal gland as the portal to what is unseen, the bridge between the body and soul. It is the shape of a pinecone, hence the name pineal gland.