12 years old in puberty belongs to the stage of chest development, generally do not need special intervention, daily attention to balanced nutrition, a good work and rest, and appropriate increase in exercise can be. 1. Nutritional balance: pay attention to the nutritional balance, it is recommended to eat some high-quality protein foods, such as fish, shrimp, milk, pig’s feet, etc., but also appropriate to eat more fresh fruits and vegetables, such as papaya, cantaloupe, broccoli, etc., through the supplementation of nutrients to promote the development of the body and breasts. 2. Adopt a good work and rest: pay attention to the usual good work and rest habits, to ensure adequate sleep, try to go to sleep before 9 to 10 o’clock in the evening. 3. Appropriate increase in exercise: appropriate increase in physical exercise, such as playing badminton, swimming, etc., can play a role in assisting breast enlargement. Chest development and genetic factors also have a great relationship, if the chest development is slow, it is recommended to go to the hospital in a timely manner, under the guidance of the doctor’s treatment, to avoid delays in the condition.