Puberty can hit teen stars hard. Just think back on the red-hot "young" careers of male soprano singers like Michael Jackson, Donny Osmond and Wayne Newton, who took years to recover from their early high-note-singing high points to make it back to the top again.
Luckily for pop-phenom Justin Bieber, he's got Usher for a mentor and a voice coach who knows her stuff. Which you can clearly see in the sneak peek from Wednesday's E! special, Justin Bieber: My World. Bieber is deep, or at least he will be soon!