Rock music originated in the 1950s in the United States and was influenced by genres like blues, folk, jazz and gospel. It grew in popularity internationally in the 1960s and diversified into new styles. The 1990s saw the rise of alternative rock and grunge and the mainstream popularity of indie rock. Modern rock music has been influenced by genres like emo, pop punk, and post-hardcore and has been a medium for social and political expression. Famous rock bands that have shaped the genre over the decades include The Beatles, The Rolling Stones, Nirvana, AC/DC, Guns N' Roses, Metallica, Queen, U2, and Green Day.