Generally speaking, it is normal for girls to develop breasts around the age of ten. Because girls enter puberty at about the same age, if they enter puberty too early or too late, most of them are abnormal. If puberty occurs too early and the breasts develop early, this is caused by precocious puberty, if the girl develops breasts before the age of eight weeks, it belongs to the category of precocious puberty. If a girl is over fifteen years old and still has no breast development, she is too late to develop. Therefore, it is normal for girls to develop breasts around the age of ten, but it is important to find the cause of premature or late development.