Activate the untapped potential of your inner eye with this guide to understanding pineal gland function and how it can improve your sleep, boost your mood, promote peak performance, and ultimately, expand your consciousness. The pineal gland, also known as your third eye, is a pea-size gland at the center of your brain. The pineal gland plays a huge role in your spiritual and physical health, from releasing melatonin to linking your consciousness to the metaphysical world.