Room to grow.

Back in the day, if a girl hit puberty before 9, doctors worried she might have hormonal problems or a brain tumor. But now, docs have some new insight for growing gals because of a study done by Pediatrics. They tested 17,000 girls between the ages of 3 and 12, and found that this generation goes through early changes like breast development, body hair and acne by the age of 6 without it ever leading to any harm. Why do some kindergarten girls still need training wheels while others need training bras? Dr. Rob Ricti believes low birth weight might be one possibility of premature puberty. "The girl's body goes into overdrive earlier in age in order to catch up for lost time," says Dr. Ricti. Some doctors believe better nutrition, ethnicity and maternal genes might be factors. Others strongly blame that puberty is knocking on some girls' doors sooner than others because Americans eat more and exercise less. "This can lead to girls storing more estrogen in their tissues," says Dr. Ricti, "leading them to develo p much earlier." Rest assured--researchers predict this wave of development won't go lower and lower in age.