An implant placed above the muscle is referred to as ‘sub-mammary’ (or ‘sub-glandular’), while an implant placed under the muscle is referred to as ‘sub-pectoral’ (or ‘sub-muscular’).The muscle in question is the pectoralis major.The term ‘sub-pectoral’ or ‘sub-muscular’ is somewhat misleading, as implants placed under the pec major are only partially covered by the muscle.The pec major covers the upper/medial half of the breast area, so a ‘sub-pectoral’ implant is truly subpectoral only in the upper and medial aspect of the augmented breast, while the lower and lateral aspect of the implant is actually in a sub-mammary position.Because sub-pectoral implants are, in reality, both sub-pectoral (upper/medial breast) and sub-mammary (lower/lateral breast), this placement has more recently been referred to as a ‘dual plane’ approach to breast augmentation.There is also ‘total submuscular’ implant placement, in which the implant is positioned behind the pec major and the serratus anterior muscle, so that the entire implant surface is covered by muscle tissue.This is not commonly done for cosmetic breast augmentations, but has been used for breast reconstruction using breast implants.