What's a natural way to grow bigger boobs without surgery?

Get Fat: Gain weight. The breasts have a great deal of fatty tissue, more as you age. While i wouldn't recommend this option from a health perspective, it is an option. Besides adding to health risks, your breasts will not get firmer or or have better shape. The only reasonable option for larger, aesthetically appealing breasts is surgery whether it be implants or fat injection after liposuction.

None: There is realy no natural way to grow your breasts. Gaining weight is not an attractive solution because your whole body gets out of shape. The only effective way to do it is with breast implants. Fat injection neccesitate multiple sessions and the enlargement is very modest.