Theodor Seuss Geisel, aka Dr. Seuss (b. 1904) was an American writer, political cartoonist, poet, animator, book publisher, and artist best known for authoring children's books. Geisel adopted his "Dr. Seuss" pen name during his university studies at Dartmouth College and the University of Oxford. He left Oxford in 1927 to begin his career as an illustrator and cartoonist for Vanity Fair, Life, and various other publications. He also worked as an illustrator for advertising campaigns, most notably for Flit and Standard Oil, and as a political cartoonist for the New York newspaper PM. He published his first children's book in 1937. During World War II, he worked in an animation department of the United States Army where he produced several short films. Geisel's early artwork often employed the shaded texture of pencil drawings or watercolors, but in his children's books of the postwar period, he generally made use of a starker medium—pen and ink—normally using just black, white, and one or two colors. His later books, such as The Lorax, used more colors. Geisel's style was unique – his figures are often "rounded" and somewhat droopy. This is true, for instance, of the faces of the Grinch and the Cat in the Hat. Almost all his buildings and machinery were devoid of straight lines when they were drawn, even when he was representing real objects.