There are anatomical differences between men and women, including proportions and size differences between various structures, which make a face look more masculine versus feminine. Typically, masculine features include lower set and square eyebrows, prominent frontal (upper eye socket) bones, deeper set eyes, and more angled and larger jaws compared with feminine features. There is also more facial muscle mass, subcutaneous tissue, and higher blood vessel density in men compared with women. A more prominent chin, defined jawline, and healthy teeth are associated with optimal male facial attractiveness across cultures. The proportions between the various facial features (e.g. forehead, nose, jaw, and chin) must be carefully measured and optimized to maintain the desirable male aesthetic.