The Nocturnes, Op. 9 are a set of three nocturnes written by Frédéric Chopin between 1830 and 1832, published that year, and dedicated to Madame Marie Pleyel. The second nocturne of the work is regarded as Chopin's most famous piece.
Chopin composed his best-known Nocturne in E-flat major, Op. 9, No. 2 when he was around twenty years old.（Source）