Located underneath the back section of the corpus callosum you can find your pineal gland. The pineal gland is a small gland found in the middle of the brain. The pineal gland secretes melatonin and helps control the cycle of sleep and wakefulness. It is believed melatonin helps synchronize circadian rhythms in various parts of the body. Out of all the different parts of the endocrine system, the pineal gland was the last organ to be discovered. The endocrine system is made up of multiple organs and glands that create and release hormones. The main job of the pineal gland is to intercept information about the day and night cycle from your eyes. The pineal gland contains specialized cells called pinealocytes that create melatonin and release it into the cerebrospinal fluid, which then takes it to your bloodstream.