Impressionism, the leading development in French painting in the later 19th century and a reaction against both the academic tradition and romanticism, refers principally to the work of Claude Monet, Pierre Auguste Renoir, and other artists associated with them, such as Camille Pissarro and Alfred Sisley, who shared a common approach to the rendering of outdoor subjects. Impressionism also refers to the work of artists who participated in a series of group exhibitions in Paris, the first and most famous of which was held from April 15 to May 15, 1874, at the studio of the photographer Nadar. The artists represented at the exhibition, or in the succeeding ones held by the group between 1876 and 1886, included Paul Czanne, Edgar Degas, Jean Baptiste Armand Guillaumin, Berthe Morisot, and, after 1879, Paul Gauguin and the American artist Mary Cassatt.

2      The term impressionism was derived from a painting by Claude Monet Impression: Sunrise (1872; Muse Marmottan, Paris), a view of the port of Le Havre in the mist and was coined for the group by the unfriendly  critic Louis Leroy. Monet probably intended the title to  refer to the sketchy, unfinished look of the work, similar to receiving an impression of something on the basis of an exposure that is partially obscured and incomplete in its detail. The term, however, was quickly taken up by sympathetic critics, who used it in an alternative sense to mean the impression stamped on the senses by a visual experience that is rapid and transitory, associated with a particular moment in time. Monet, Renoir, Pissarro, and Sisley were impressionists in the latter sense; beginning in the later 1860s and culminating in 1872-75, they chose to paint outdoors (en plein air), recording the rapidly changing conditions of light and atmosphere as well as their individual sensations before nature. They used high-key colors and a variety of brushstrokes, which allowed them to be responsive both to the material character and texture of the object in nature and to the impact of light on its surfaces.

3      If the term impressionism is used to indicate a concern for contemporarysubject matter of an informal and pleasurable kind especially aspects of the social life of Paris and its environs and a technique and organization that gives an impression of casualness or spontaneity, then it includes not only the work of Degas and Morisot, but also that of douard Manet. He did not exhibit with the group, but works such as his Djeuner sur l'herbe (1863; Muse d'Orsay, Paris) had an important influence on the younger painters during the 1860s. During the early 1870s, Manet was on friendly terms with the impressionists and adopted some of the same outdoor subjects.

4      Finally, when impressionism is extended to cover the early work of Gauguin and Cassatt, it reflects an influence of impressionism on a slightly younger group of artists, in their color range, brushwork, and approach to nature.

5      By the early 1880s the feeling of cohesiveness that had originally brought the impressionists together had begun to dissolve under the pressure of factions and rivalries. The sense of a shared approach to nature among the  landscape painters had also dissolved by then, so that the artists increasingly took their own individual directions. At the same time, impressionism was beginning to have a tremendous impact both on French painting generally and also on the art of other countries; this continued well into the 20th century. Either directly or through the intermediary of the developments of the 1880s, such as neoimpressionism and postimpressionism, impressionism influenced modern art in such fundamental features as a loosening up of brushwork, which abolished finally the traditional distinction between the finished painting and the preliminary sketch or study; a concern for the two-dimensional surface of a painting, which is defined by the patterns and feeling of movement of the paint on the ground; and a use of pure, bright colors.

6      In 1991, the news that two of Russia's major museums, the Hermitage Museum in Saint Petersburg and the Pushkin in Moscow, had secretly stored a group of impressionist and postimpressionist paintings part of a vast collection looted from Germany by the Union of Soviet Socialist Republics (USSR) in the final months of World War II came as a revelation to the art world. Most of the paintings had come from private collections (some had previously been looted by the Nazis; see Holocaust; Nazism) and had not been seen in public for many decades. A few had never been exhibited; a few were believed to have been destroyed. Both museums exhibited many of these works, including paintings by Degas, Renoir, Gauguin, and Monet, in 1995.