19. MattyB: 21 Under 21 (2013)

Matty B

Last Year's Rank: N/A

Birthdate: January 6, 2003 (Age 10)

Why He's Hot: Matthew Morris is standing pretty tall for a kid that's yet to have grown to five feet. The rapper known as MattyB has done plenty with his first 10 years on earth -— releasing several singles and garnering attention from the likes of NBC's "Today" and "Entertainment Tonight." Whether he's plotting on what young lady he's going to bless by draping her with his letterman jacket on "My First Girlfriend" or selling out theaters during his current spot-date tour, it's clear that the kid is in demand. And did we mention that Matty's YouTube channel boasts more than 658 million video views. The Atlanta native is still unsigned, but trust: execs are calling in to recruit the young talent with Bieber-esque looks and, yeah, maybe the potential to be just as big.