Chopin Nocturne in C sharp minor B.49 Op .posth. Lento con gran espressione

The Nocturne No. 20 in C♯ minor, Op. posth., Lento con gran espressione, P 1, No. 16, KKIVa/16, is a solo piano piece composed by Frédéric Chopin in 1830 and published in 1870.
Chopin dedicated this work to his older sister Ludwika Chopin, with the statement: "To my sister Ludwika as an exercise before beginning the study of my second Concerto". First published 21 years after the composer's death, the piece is usually referred to as Lento con gran espressione, from its tempo marking. It is sometimes also called Reminiscence.