The Post-Impressionists developed out of the movement of Impressionism, but felt it necessary to more systematically examine the properties and expressive qualities of line, pattern, form, and color. Vincent van Gogh, Paul Gauguin, Georges Seurat, and Paul Cezanne were leaders of this movement. 

While Expressionism, of which Ernst Ludwig Kirchner's Self-Portrait as a Soldier is emblematic, was highly significant and powerful in the 1920s' Weimar Republic, political changes also changed artistic tastes. When Adolf Hitler and the Nazi Party took power in the 1930s, they targeted this kind of art for its association with bohemian lifestyles, intellectualism, and Jewish culture. In 1938, this piece of art was included in a famous exhibition of "Degenerate Art" put on by the Nazis. With such persecution, Kirchner's consistent mental health issues again came to the fore, and he committed suicide in 1938 by gunshot.

Image is in the public domain, accessed through Wikipedia Media Commons: https://commons.wikimedia.org/wiki/File:Kirchner_-_Selbstbildnis_als_Soldat.jpg

The Goldfish is, fitting with Henri Matisse's work generally, an abstract piece, but one whose general forms and shapes are somewhat representational. Heightening the slight abstraction of the painting's shapes is the choice of color palette made by Henri Matisse. The bright, almost unnatural colors create a different perspective for the viewer and match more closely to other forms of abstract art.

The eclectic, improvisational nature of jazz had a wide influence in other artistic forms. In particular, visual artists sought to take some of jazz's extemporaneous elements and apply them to painting and sculpture. This idea greatly influence Jackson Pollock's "drip method" and other aspects of Abstract Expressionist art from the 1940s and 1950s.

Marilyn Diptych (1962) gets its form from early Christian diptych paintings that presented two images side by side. It was created using silkscreening, a method not used by early Christian painters. None of Warhol's Marilyns were made in the mosaic, relief, or fresco styles.

This portrait of Adele Bloch-Bauer resembles The Kiss and other famous Klimt works. The rest are other Austrian artists.

Work is in the public domain, image accessed through WikiArt: http://www.wikiart.org/en/gustav-klimt/portrait-of-adele-bloch-bauer-i-1907-1

German forces seized the painting and, after the war, Adele Bloch-Bauer's husband Ferdinand sought to have it returned to his nieces and nephews. A long court battle followed, and it was only in 2006 that Austria returned it to the family.

Work is in the public domain, image accessed through WikiArt: http://www.wikiart.org/en/gustav-klimt/portrait-of-adele-bloch-bauer-i-1907-1

The Mexican Mural Movement was Mexican painting movement that developed from the 1920s to the 1950s. Its most well-known painters were Diego Rivera, José Clemente Orozco, and David Alfaro Siqueiros. Each of these men were heavily influenced by Marxism and a sense of Mexican nationalism, which made them want to paint historical, indigenous, and agricultural scenes. Most of the muralists were often skirting trouble with the changing governments in Mexico, finding their support fluctuating throughout their careers.

Official Catholic record states that San Juan Diego, then just a peasant, witnessed an apparition of the Virgin Mary four times at the Hill of Tepeyac, now a suburb of Mexico City.  It is said that the apparition of the Virgin Mary spoke to him in his native tongue of Nahuatl, asking for a church to be built there in her honor. Now the Basilica of Our Lady of Guadalupe is the most visited Catholic pilgrimage site in the world, and the world's third most-visited sacred site.

Diego Rivera is a very well-known Mexican artist. One of his many artistic accomplishments was to help launch Mexican muralism in the 1920s. Although Mexico has a long history of mural art, Mexican muralism gained traction as a globally popular art form thanks to the contributions of Rivera and other artists, such as José Clemente Orozco and David Alfaro Siqueiros, as they used the form as a political and social tool. In the USA, Mexican muralism served as inspiration for the Chicano art movement.