Cranial Nerve III, also known as the oculomotor nerve, is one of the twelve cranial nerves. It primarily controls most of the eye's movements, including the ability to raise the eyelid and adjust the size of the pupil. This nerve is essential for proper vision and eye coordination. The oculomotor nerve originates in the midbrain and extends to the eye muscles. It innervates four of the six extraocular muscles, which are responsible for moving the eyeball. Damage to this nerve can lead to symptoms such as double vision, drooping eyelids, and difficulty focusing.