There are no accurate standards to measure the breast development of a 10 year old girl because of the variation in breast development between individuals. If a girl develops too early, her breasts may be slightly raised and hemispherical, while if she develops too late, her breasts may not be raised and may only have a normal breast shape. Usually, it is normal for girls to start developing their breasts between the ages of 8 and 13. Parents should pay attention to the development of girls in a timely manner and seek medical intervention if their breasts do not develop at the age of 13 or if their breasts expand. Most girls enter puberty at the age of 10-13, and their secondary sexual characteristics begin to develop gradually due to the influence of sex hormone levels, with pubic hair, axillary hair, menstruation and breast development gradually appearing. At the early stage of breast development, it is normal to feel slight itching and swelling of the breasts. After 3-5 years of maturation, the breasts become hemispherical in size, the nipples become cylindrical in size, and the areolas and nipples deepen in color. Parents at this time can teach 10-year-old girls to start learning to protect their breasts, if the nipples are too prominent, should choose loose, breathable cotton sports underwear, do not wear too binding underwear, so as not to affect breast development, and even compression of the heart and lungs, resulting in poor blood circulation. In addition, it is recommended that after wearing underwear, you need to use your hands to gather both sides of the breast to the middle for a while, to promote the development of the breast to both sides of the median line. Underwear needs to be changed and washed regularly to ensure hygienic and clean breasts, which is beneficial to breast development. Parents should also pay attention to remind girls to ensure sleep and avoid staying up late during this period. Nutritional aspects to ensure a balanced intake, eat more fresh vegetables and fruits, reduce the consumption of spicy, fried, barbecued and other stimulating foods, so as not to affect the development.