Leonardo da Vinci was a gifted painter, talented musician, and dedicated scientist and inventor, designing flying machines, submarines, and even helicopters.  Yet he had a hard time finishing things, a problem anyone can relate to.  Only thirteen paintings are known to be his, as for the illustrated encyclopedia he intended to create, all that he left were thousands of disorganized notebook pages.  Here is an accessible portrait of a fascinating man who lived at a fascinating time—Italy during the Renaissance.