The breast is composed mainly of mammary glands, connective tissue and fatty tissue. The difference between mammary glandular breasts and fatty breasts is, as the name implies, related to the proportion of the main tissue components. Mammary glandular breasts have a larger proportion of mammary glands and less fatty and connective tissues, which are dense, firm and elastic. Fatty breasts are soft, easy to sag and will collapse when lying down. After menopause and breastfeeding, most of them will be converted from mammary breasts to fatty breasts. Both mammary and fatty breasts are related to genetic factors and cannot be changed by medication, exercise or other treatments.