"La Bella Principessa" was a wedding portrait of Bianca Sanseverino. It was done done for her wedding book in 1496. Bianca,was "the illegitimate daughter of Ludovico Sforza, who was Leonardo's employer at the time.
This may be one of the first pastel portraits ever done.
Leonardo probably learned the
Trois crayons (red, white, black chalks )method
from the French artist
who he met
in Milan, Itly,
La Bella Principessa