Lichtenstein's comic book style is characterized by the use of a dot pattern, known as the Benday dot. He started using this system in 1961, and, although it became a signature element of his art, the system had been invented in 1879 and had already been used in comics, newspapers and billboards. Lichtenstein made the dots very big, almost to the point of exaggeration. The use of thick lines, as well as the bright colors are also elements that appear in billboards and comic books.