Age: 17
Occupation: Pop star
Previous TIME 100 appearances: 0
Justin Bieber, for those of you who don't have teenagers at home, is spelled O-M-G. The former YouTube sensation is now the most squealed-over pop star since David Cassidy: fans track him obsessively on Twitter, where he has more than 8 million followers; his sophomore album, My World 2.0, has sold more than 2 million copies; his concert film and documentary Never Say Never hit theaters in February and has grossed more than $80 million worldwide. (If you think that's pretty impressive for a teenager, did we mention he's already released his autobiography, Justin Bieber: First Step 2 Forever?)