Pablo Picasso is often credited as the first Abstract artist. Picasso and Georges Braque developed the Cubist method between 1908 and 1912. Picasso's "Les Demoiselles d'Avignon" is arguably the most famous Cubist painting. Cubism sought to capture a subject, or parts of a subject, from many different angles or viewpoints at once.
Expressionism also became very popular in the first years of the twentieth century. It is a very broad category, but generally it involves the artist's attempt to portray a mood or feeling using color, imagery, shadow, brushstrokes, etc. Rather than creating a likeness, the artists distort images to capture an idea, often concerning human suffering. Vincent Van Gogh and Edvard Munch are ideal examples of early Expressionists.
Dada (1916 to 1922) was a movement of artists largely focused on protesting World War I. Dada philosophy was nihilistic, declaring that traditional art was no longer effective in moving people, and had become bourgeois and hollow. Many Dada artists went on to establish Surrealism in Europe and the United States in the 1920s and 1930s. Surrealism was based on the principles and symbols of Freud's psychoanalysis and free association. Surrealists believed they could create art out of tapping into the unconscious mind.
During World War II, many European artists emigrated to America, one reason New York City became the hub of modern art in the mid-twentieth century. The 1950s introduced Abstract-Expressionism, a form that essentially did away with any semblance of the figurative. Artists Mark Rothko, Jackson Pollock and Franz Kline are the most well-known practitioners of this style. Their art was mainly concerned with color and methods of paint application. Pollock was known for his "drip paintings," in which he would pour or drip paint onto the canvas and then manipulate it with various tools.
The Abstract tradition continued on with Pop artists like Andy Warhol, who used symbols like the Campbell's Soup can to make a statement about cultural symbolism. Minimalism breaks art down to its fundamental parts, focusing on shapes, lines or particular objects. Performance Art and Video Art are generally considered to be Abstract art, as is graffiti, and a lot of photography as well.