The pineal gland is a small endocrine gland positioned posterior to the third ventricle and inferior to the splenium of the corpus callosum. Throughout history, many mystics and psychics have called it the “third eye,” while others give it this name because of how sensitive it is to light. The major function of the pineal gland is to produce melatonin in response to light or darkness in the environment. Calcification of the pineal gland is common in older age, and often called “brain sand.”