The sternocleidomastoid muscles, often abbreviated as SCM, are a pair of long, thick muscles located on either side of the neck. They get their name from their attachments to the sternum (sterno-), clavicle (cleido-), and mastoid process of the temporal bone (-mastoid) behind the ear. The sternocleidomastoid muscles have a crucial role in head movement and neck stabilization. When both sides of these muscles contract, they flex the neck and bring the chin toward the chest. When one side contracts, it tilts the head to the opposite side and rotates it.