Blues was born in the late 19th century in the Mississippi Delta as a musical expression of African Americans' suffering. Emerging from work songs and spirituals of the slavery era, the genre developed through legends like Robert Johnson, B.B. King and Muddy Waters. The standard 12-bar form, characteristic "blue notes" and heartfelt lyrics are distinctive features of blues. In the 1950s, blues met electric instruments in Chicago and paved the way for rock'n'roll. White musicians like Eric Clapton and Rolling Stones introduced blues to the world. Today, blues continues to exist as one of the cornerstones of modern music genres.