The development of breast nuclei in girls at the age of 9 is generally not considered a sign of precocious puberty if this symptom is the only one present. It is usually considered that precocious puberty in girls refers to the appearance of secondary sexual characteristics before the age of 8. After the onset of puberty, development continues to follow a certain pattern, in the order of breast development, changes in pubic hair and external genitalia, onset of menstruation and axillary hair. Accelerated growth in height and weight can occur during this period. Breast nucleus development in a 9-year-old girl is generally not considered precocious and is normal sexual development. The age at which a child develops depends on when the hypothalamic-pituitary-gonadal axis function is initiated, which usually begins around 10 to 12 years of age in girls, and the whole process lasts 1.5 to 6 years, with an average of 4 years. If the child has other manifestations in addition to the development of the breast nucleus, it is recommended to visit a regular hospital for a comprehensive assessment and judgment by a specialist.