Breast cancer, as one of the cancers that cause great harm to women, has brought great pain to the majority of female friends. Many female friends do not actually know much about breast cancer, in fact, in the early stage of breast cancer development, it can be detected through self-examination. Self-examination of breasts is the most basic way to prevent and detect breast cancer at an early stage. For women with normal menstruation, the best time for breast self-examination is the 3rd-7th day after menstruation, when the effect of estrogen on the mammary gland is minimized, and the mammary gland is in a relatively static state, which makes it easier to detect lesions. Post-menopausal middle-aged and elderly women, due to the reduction of estrogen in the body, the influence of endocrine hormones is also relatively weaker, and thus can choose the time of self-examination at will.