Leonardo, like Christopher Columbus, possessed an greedy curiosity and desire for discovery of unknown worlds. Only observation, says many times Leonardo, is the key to knowledge and understanding. His drawings are unlike from those of his generation and those drawn before and after him. Among them are fast sketches, portraits, rapid notes for compositions, complicated cartoons, drapery studies, and projects for machines, plants, animals, sketched from nature and anatomical studies. The grotesque caricatures are combinations and variations of human faces, creating a series of types. His anatomical sketches make obvious not only the place of muscles or the bone construction; they as well illustrate the embryo in mother's womb and a exposed skull, - symbols of the creation and ending of human life.