Some of Leonardo da Vinci drawings show the "sfumato" technique to render realistic effects. It is in this period that Giotto's realism lessons ( and also Cavallini's, , Duccio's and Masaccio's ) are enhanced to even more spectacular levels.
Leonardo da Vinci, Study of Arms and Hands. c. 1474.
Pen and Ink with white chalk on brown paper
Leonardo, cartoon, national gallery (c. 1499-1500)
Head of a Young Woman , Accademia di Belle Arti, Venice
Head of the Vergin, 1508-1512, MET New York
Here follow some pictures taken from this website
Study of woman
Study of Woman
Drawing for the Battle of Anghiari
Peter Paul Ruben's copy of the Battle of Anghiari by Leonardo (original lost) , c. 1603 - click to enlarge
The Battle of Anghiari Details - click to enlarge
Study of Horses with riders
Study of horse and rider
Probably a sketch for the equestrian monument of the his mentor and patron Ludovico Sforza's father, Francesco Sforza, which he never made.
A landscape study. Landscape as a gendre was not yet established as a form of art. Landscape painting begun with the invention of color-tubes in the 19th century which allowed painters to carry colors outside their studios and paint "en plein air".
Self-portrait - ca. 1512-1515
The Chiaroscuro is a technique which manipulates the shades. It was known in the ancient Greece (Apollodoro, Polignoto of Thasos).
Leonardo modified it in a "sfumato" technique which renders the passing from light to dark softer.
check the website about Leonardo Inventions