What IS puberty? When they start to grow hair or something else?

Alison Scott, pediatrician: “Puberty is a transition between childhood and adulthood– your body is getting ready for reproduction (a totally terrifying idea, I know). It’s the biological change that the body goes through to transition from a child to a grownup. The real first sign of puberty for girls is breast development, and for boys it’s testicular enlargement. Those are the physical changes that mark the onset of puberty. Hair and smell are much easier to notice, of course– but biologically that’s not when the time clock really starts. Puberty also has a lot to do with brain development. The brain is doing a lot of remodeling during these years. Sometimes you might notice mood changes first: around 9 girls will get more moody, and that might be what you see first. For boys, getting quieter– and sometimes more angry– happens when testosterone starts flooding the system. Puberty is a long process, spanning roughly 3 years, but exactly when it starts for each kid is unique.”