(Untitled) When Do Breasts Start Growing? Breasts can start growing as early as age 8 or as late as 13. Some girls' breasts grow slowly and others grow quickly. Some girls may feel like their breasts will never start growing. But it's just that girls start developing at different ages and different rates. One girl might have more developed breasts at 12, whereas her friend could be still flat as a board. If you want something special so log on to . www.smartmasti.com http://www.smartmasti.com