Breasts grow naturally during puberty and can change throughout the course of your life. They usually start developing when you're between the ages of 8 and 13, but they can continue to grow into your early twenties and can change size and shape due to age, weight and pregnancy.[1] Although the size of breasts is mostly determined by your DNA, other factors, such as weight, muscle mass, and age, can affect their appearance. Although the best solution is to wait and give your breasts time to grow, you can also try a few different methods to enhance them naturally, including eating certain foods and doing particular exercises.