I'm 19 years old girl. My problem is my boobs have not developed into fully mature breast. What can I do to get them to grow?

In general, female breasts stop developing at around 18 or 19 years old. This is when a primary level of maturity is achieved, however further changes occur with pregnancy and lactation (the production of breast milk). Your breasts will continue to change throughout your life, as the signs of aging become more apparent. For example, your breasts may begin to droop as supportive tissues weaken, or grow larger when you gain weight.Breast augmentation with implants is the safest and most effective way to enlarge the size of your breasts.

  Dear autumn1514, Most women have developed all the breast tissue they are going to have by 19 years old. It is unlikely you will see any more maturation after this age. You should discuss breast augmentation with a board certified plastic surgeon in your area if you wish to enhance what you already have. Good luck. Dr. Gervais

By age 19 your breast growth is probably complete. There is no medication or topical treatment to increase the size of the breast. If you want to be larger consider a breast augmentation.