Superficial muscular aponeurotic system (SMAS) is a thin yet tough unitary tissue plane of the face formed by facial fasciae, subcutaneous connective tissue, and facial muscles. Its composition varies, containing muscle fibres in some areas, and fibrous or fibroaponeurotic tissue in others. It connects to the dermis via vertical septa. It does not attach to bone. In most areas, a distinct plane can be defined deep to the SMAS.