Selective Estrogen Receptor Modulators (SERMs) are a class of drugs that act on the estrogen receptor with a dual action, serving as agonists or antagonists depending on the target tissue. This means they can mimic the action of estrogen in some tissues (such as bones) and block the action of estrogen in others (like breasts or the uterus). SERMs are used to treat and prevent various conditions, including breast cancer, osteoporosis, and some cardiovascular diseases. Their selective ability allows for the beneficial effects of estrogen in certain parts of the body without the negative effects associated with estrogen therapy, such as an increased risk of breast cancer. Examples of SERMs include tamoxifen and raloxifene.