Rap first became popular in the 1970s as a street art form among African American teenagers. The Sugarhill Gang's 1979 hit "Rapper's Delight" brought rap into the mainstream. In the 1990s, rap matured from simple old-school lyrics to louder new-school styles featuring more complex lyrics from artists like The Notorious B.I.G., Snoop Dogg, and Tupac. Rap involves speaking or chanting rhyming lyrics, often set to a beat, and addresses topics like sex, violence, and politics through sophisticated poetic rhymes.