U2 formed in Dublin in 1976, when none of the members were very good musicians. However, they got better as they got older. They were more popular for playing live shows than for releasing albums. This changed with their hit record in 1987, "The Joshua Tree". In 1991, U2 released a new album called "Achtung Baby". This album sounded very different from their other albums because it was inspired by alternative rock and dance music. "Achtung Baby" and its worldwide Zoo TV Tour were both very popular. U2 experimented for the rest of the 1990s, making two other very different albums, "Zooropa" and "Pop". 