The Longissimus is a muscle located in the back, part of the larger group known as the erector spinae. It plays a crucial role in maintaining posture and supporting the spine during movement. The Longissimus extends from the lower back to the upper back and neck, allowing for actions such as bending and twisting. This muscle is divided into three sections: the Longissimus thoracis, which runs along the thoracic spine; the Longissimus cervicis, which extends to the cervical spine; and the Longissimus capitis, which connects to the skull. Strengthening the Longissimus can help improve overall back health and stability.