In 2009, Bieber toured with Iyaz and Taylor Swift, and traveled in the United States. His first album, "My World", which was released in that year, features four singles, "One Time", "One Less Lonely Girl", "Favorite Girl", and "Love Me". He signed to a record deal with Usher. He released "My World 2.0" in March 2010 as his second album, as well as going on a world tour. The album includes his smash hit single "Baby" featuring Ludacris, a remix version of "Somebody to Love" featuring his mentor Usher, and two promotional singles "U Smile", and "Never Let You Go". In the same year, he released "My Worlds Acoustic", which includes acoustic versions of his songs from the "My World" album and it also contains the ballad song "Pray". "Purpose"'s single "Sorry" is his most popular song.