He's from the cold Canadian north, but Justin Bieber has been melting tween girls' hearts for months now with R&B-flavored singles from his debut album. Call it Bieber Fever.

Though that album, "My World," came out Tuesday, the 15-year-old's career got rolling a couple of years ago, thanks to his mom. She posted videos of a singing Bieber on YouTube to share with the family . . . and almost 90 million hits later he had four songs in Billboard's Hot 100 - that's before "World" dropped.

In between YouTube and the album, the Ontario native was discovered by industry exec Scooter Braun.

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They flew to Atlanta to sing for Usher, who later won a bidding war against Justin Timberlake to sign the teen. Bieber also plays drums, guitar, piano and trumpet. And hockey, of course.

When Billboard magazine asked him about the songs on "My World," Bieber said: "Most are about love and stuff that girls can appreciate."