How to correct uneven breasts? 21 years old. (photos)

You have clearly been living with this difficult situation since early adolescence and although very common and recognized amongst plastic surgeons, pediatricians, and gyn's, this is less understood and recognized by patients. Please know that you are not alone, and you can be helped. Your right breast has simply underdeveloped and at age 21 we can fully expect that this situation is stable and unlikely to change without surgery. 
During a face to face consultation with an experienced board certified plastic surgeon all of your options can and will be reviewed. If you are happy with your left breast and would like the right breast to be as close as possible to your left breast, you will almost certainly require the placement of a tissue expander on your right side to get the skin stretched adequately to allow for a proper implant placement. If you feel you would like your left breast to be a bit smaller, it is possible that a small reduction can be performed on the left breast with a one stage augmentation of your right. Your right side also has a tuberous breast deformity that would require a correction of the protruding subareolar tissue with a circumareolar mastopexy. 
There are many excellent plastic surgeons with whom you can consult. do your research, be open to the idea of more than one consultation, review before and after galleries, and find the plastic surgeon with whom you feel confident. In severe cases such as yours, sometimes the insurance company will consider this "medically necessary" and almost in the "reconstructive" realm rather than cosmetic. That would be up to your plastic surgeon and his or her staff to try to get this approved by your insurance company. 
Best of luck to you. 

The asymmetry of your breasts is uncommon, but not rare, and most experienced plastic surgeons have treated patients like yourself. You will need an implant in the right breast. For the best symmetry, you will need an uplift of your left breast as well because your left nipple is lower than your right nipple. Implanted breasts do not look entirely like natural breasts, so you may also need a small implant in your left side.The above is a simplification of treating your issue. You must see an experienced, board certified plastic surgeon for a treatment plan. Various implant sizes and procedures will be discussed with you by your PS.Thank you for your question and photos, and best of luck to you.

Due to the significant amount of asymmetry, this is not an easy case.  Also, it appears that you may be tuberous on the right side which makes this even more challenging. Although your best approach is to meet with a Board Certified Plastic Surgeon in person, from the photos I would recommend the following:Peri-areolar sub muscular augmentation on the right side with possible scoring of the lower pole to allow for glandular releaseBreast lift on the left side to raise the nipple position and adjust the breast volume upwards to match the new breast on the right.  Keep in mind that it may take another surgery to create even more optimal symmetry since your breasts may continue to grow and change even after surgery.I hope that helps and wish you the very best!Gregory A Buford MD FACSBoard Certified Plastic Surgeon and Author