The main features of breast development in girls include nipple projection, areola enlargement, breast enlargement and breast pain. 1. Nipple bulge: When a girl’s breasts start to develop, there will be a nipple bulge, and with the nipple bulge, the nipple will gradually increase in size. 2. Enlargement of areola: When a girl’s breasts develop, the areola around the breasts will also enlarge gradually. Some girls’ areola will become thicker and cover a larger area, and the color of the areola will also become darker. 3. Breast enlargement: Breast enlargement is the most obvious characteristic of girls’ breast development, but the degree of enlargement varies from person to person. At this time, the breasts will be larger than before, usually in a semicircular shape. 4. Breast pain: When a girl’s breasts are developing, estrogen will be secreted in large quantities, which will stimulate the glands to proliferate, leading to the symptom of breast pain. It is recommended that girls go to the hospital in time when breast discomfort occurs, and under the guidance of the doctor for related treatment.