It may be normal for a 12 year old girl to have undeveloped breasts, and there is no need for any special treatment. You can improve your breasts through food, exercise, and a good work routine, and if you fail to do so, we recommend that you seek medical attention. Generally, breasts begin to develop when a woman is close to 10 years old, and it takes about 3 to 5 years for them to reach maturity. Some individuals may develop a little slower. Observation can be made through the following measures: 1. Food: Eat more food rich in plant protein, such as peanuts, walnuts, almonds, etc., and food rich in animal protein, such as beef, eggs, milk, etc.. You can also consume more foods rich in vitamins and trace elements, such as cantaloupe, kiwi, fish, lamb, etc., to promote body and breast development in terms of supplemental nutrition. 2. Exercise: It is recommended that appropriate physical exercise, more outdoor activities such as running, jumping rope, playing badminton, etc., you can also choose to expand the chest exercise, swimming, etc., can promote the growth and development of the body. 3. Adopt a good work and rest: the body development period should also pay attention to the sleep situation, try to go to sleep before 9 to 10 o’clock at night, because the growth hormone to promote adolescents is secreted at night. Girls breast development is slow may also be related to the body estrogen, after more than six months of observation, such as no development, it is recommended that parents take their children to the hospital in a timely manner to do the relevant examination, so as not to delay the condition.