The opera buffa Così fan tutte (Thus do they all )is one of the three Mozart operas for which Da Ponte wrote the libretto. The other two Da Ponte-Mozart collaborations were Le nozze di Figaro and Don Giovanni. The duet Il core vi dono (I give you my heart) is sung in the second act by Dorabella and Guglielmo. Guglielmo attempts to woo Dorabella. She does not resist strongly, and soon she has given him a medallion (with Ferrando's portrait inside) in exchange for a heart-shaped locket.