To check if a girl’s mammary glands are precocious, you can look for an enlarged nipple, as well as hyperplasia of the breast tissue, such as an enlarged areola and the formation of a breast nucleus. Girls usually enter puberty around the age of 10 to 12, and if secondary sexual characteristics appear before the age of 8, it is considered precocious puberty. To check if a girl’s mammary glands are developing prematurely, you can look at the development of the nipples, if there are basic symptoms such as enlarged nipples, enlarged areola, and nucleus formation. If you suspect that a girl’s mammary glands are developing prematurely, you can go to the hospital for further tests, such as ultrasound to see if the uterus and ovaries are enlarged or to check for sex hormones. Parents of younger girls who show signs of early breast development should follow up and observe their babies, and take them to the hospital for checkups.