Born in Florence, where he studied in the Academy of Fine Arts, Lessi began his career as a watercolorist. Between 1880 and 1896, he lived in Paris, where he painted his major works. To this period belongs the Galileo e Viviani, which was exhibited in 1893 in the Champs Élysées Salon and was awarded a Gold Medal. He returned to Florence, where he lived a very secluded life. His final years were completely dedicated to the illustration of the Giovanni Boccaccio's (1313-1375) Decameron for the publisher Alinari.