The Beginning
The first stage of a girl's breast growth actually takes place before puberty. Before the age of 10 a girl's body is gearing up to start maturing and she's growing in all areas. When she reaches an age between 8 and 13 the maturing process gets under way. The first visible signs of breast growth are breast buds, which herald the onset of puberty. The breast buds grow in preparation for the ducts that the female body will need. Some conditions, such as obesity, can cause this process to happen at a younger age for some girls.