Billboard's '21 Under 21: Music's Hottest Minors 2012' list makes it official. Justin Bieber is at the top. He is currently prepping for his world tour and just rapped up the music video for "Beauty and the Beat" featuring Nicki Minaj. The guys in the British Boy Band One Direction are at #2. And Demi Lovato is currently an 'X Factor' and recently hit #1 with her single, "Give Your Heart A Break".