Abstract Expressionism was a post-World War II art movement characterized by nonrepresentational and emotionally expressive styles. There were two main types: color field painting, which used large areas of flat color; and action painting, where paint was spontaneously dripped or smeared onto the canvas to show the physical act of painting. Major artists included Helen Frankenthaler, who pioneered color field painting techniques like soak staining, and Jackson Pollock, who specialized in drip paintings and was a pioneer of the abstract expressionism movement overall.