Under normal circumstances, the human body symmetrical growth of organs, the size is not completely symmetrical, growth and development will be affected by a variety of factors during the growth and development of bilateral mammary glands slightly difference in size, is normal, wearing underwear, no difference, do not need treatment. If there is a difference between the two sides of the mammary glands, it is considered to be caused by the different sensitivity of the mammary receptors to hormones. If you are in the period of pubertal development, try to go to regular hospitals, and be treated under the guidance of the doctor, and if the pubertal development is over, it can be corrected by wearing orthopedic underwear. At present there is no special drug that can promote the development of the mammary glands, the only effective way is surgical breast augmentation orthopedic treatment, through the surgery to correct the smaller side of the mammary glands, can be implanted with fillers to fill in or use autologous fat grafting, breast augmentation surgery is risky, you need to go to the regular a little bit bigger hospital consulting.