For boys, puberty starts when the brain sends a signal to the testicles to produce testosterone. A growth spurt is often the first sign of puberty in boys, and like girls, your son's feet, hands, arms and legs may grow faster than the rest of him, causing clumsiness. For many boys, the growth peaks about two years after the beginning of puberty. His shoulders will broaden and his muscles will get bigger. Many boys have some slight swelling under the nipples, which is temporary. Testosterone affects the larynx, causing the voice to crack and then deepen. Pubic, facial, body and underarm hair will begin to grow. Like girls, oil production in the skin increases, which can lead to pimples, and sweat increases too. The penis and testicles get larger and an increase in sex hormones leads to erections, which often happen whether sexually aroused or not, as well as "wet dreams" or nocturnal emissions. Sperm production begins too.

How he might be feeling. Not surprisingly, boys may have mixed feelings about puberty too, especially since their rite of passage perhaps isn't as formalized as girls' is (after all, the "buying the first razor" trip does not compare to the "buying the training bra" shopping expedition and the "getting your period" drama in popular culture). Penis size is a common concern. As author Lynda Madaras puts it, "I thought girls were obsessed about breast size, until I wrote a book for boys and got a ton of letters about penis size!" Like girls, many boys are worried about not maturing at the same time as their friends, as well as body size, height and muscle development-in other words, feeling like a little kid amongst strong locker room giants. Involuntary erections and wet dreams (which are in part related to changing hormone levels, and don't necessarily indicate a sexual dream) can be embarrassing. Boys may also be self-conscious about cracking voices, temporary swelling under the nipples, and uneven testicles (all perfectly normal of course). Lastly, as hormones ebb and flow, emotions can show up as frustration and aggression.