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"Baby" is a song by Justin Bieber. It was released as the lead single from his debut album, "My World 2.0". The track was written by Bieber together with Christopher "Tricky" Stewart and Terius "The-Dream" Nash, both of whom worked with Bieber on "One Time", and also by R&B singer Christina Milian and labelmate, rapper Ludacris. It was available for digital download on January 18, 2010.