These artists became dissatisfied early in their careers with academic teaching's emphasis on depicting a historical or mythological subject matter with literary or anecdotal overtones. They also rejected the conventional imaginative or idealizing treatments of academic painting. By the late 1860s, Manet's art reflected a new aesthetic—which was to be a guiding force in Impressionist work—in which the importance of the traditional subject matter was downgraded and attention was shifted to the artist's manipulation of colour, tone, and texture as ends in themselves. In Manet's painting the subject became a vehicle for the artful composition of areas of flat colour, and perspectival depth was minimized so that the viewer would look at the surface patterns and relationships of the picture rather than into the illusory three-dimensional space it created. About the same time, Monet was influenced by the innovative painters Eugene Boudin and J.R. Jongkind, who depicted fleeting effects of sea and sky by means of highly coloured and texturally varied methods of paint application. The Impressionists also adopted Boudin's practice of painting entirely out-of-doors while looking at the actual scene, instead of finishing up his painting from sketches in the studio, as was the conventional practice.

In the late 1860s Monet, Pisarro, Renoir, and others began painting landscapes and river scenes in which they tried to dispassionately record the colours and forms of objects as they appeared in natural light at a given time. These artists abandoned the traditional landscape palette of muted greens, browns, and grays and instead painted in a lighter, sunnier, more brilliant key. They began by painting the play of light upon water and the reflected colours of its ripples, trying to reproduce the manifold and animated effects of sunlight and shadow and of direct and reflected light that they observed. In their efforts to reproduce immediate visual impressions as registered on the retina, they abandoned the use of grays and blacks in shadows as inaccurate and used complementary colours instead. More importantly, they learned to build up objects out of discrete flecks and dabs of pure harmonizing or contrasting colour, thus evoking the broken-hued brilliance and the variations of hue produced by sunlight and its reflections. Forms in their pictures lost their clear outlines and became dematerialized, shimmering and vibrating in a re-creation of actual outdoor conditions. And finally, traditional formal compositions were abandoned in favour of a more casual and less contrived disposition of objects within the picture frame. The Impressionists extended their new techniques to depict landscapes, trees, houses, and even urban street scenes and railroad stations.

In 1874 the group held its first show, independent of the official Salon of the French Academy, which had consistently rejected most of their works. Monet's painting “Impression: Sunrise” (1872; Musée Marmottan, Paris) earned them the initially derisive name “Impressionists” from the journalist Louis Leroy writing in the satirical magazine Le Charivari in 1874. The artists themselves soon adopted the name as descriptive of their intention to accurately convey visual “impressions.” They held seven subsequent shows, the last in 1886. During that time they continued to develop their own personal and individual styles. All, however, affirmed in their work the principles of freedom of technique, a personal rather than a conventional approach to subject matter, and the truthful reproduction of nature.

By the mid-1880s the Impressionist group had begun to dissolve as each painter increasingly pursued his own aesthetic interests and principles. In its short existence, however, it had accomplished a revolution in the history of art, providing a technical starting point for the Postimpressionist artists Paul Cézanne, Edgar Degas, Paul Gauguin, Vincent van Gogh, and Georges Seurat and freeing all subsequent Western painting from traditional techniques and approaches to subject matter.

In music, Claude Debussy (Debussy, Claude) has always been considered the principal Impressionist. Even though Debussy was influenced by the general aesthetic attitudes of Impressionist painters, he made no attempts to compose with musical techniques that were closely analogous to techniques of painting. Furthermore, the characteristics of Debussy's music are so variable from the first through the last of his compositions that even a general sense of Impressionism might best be restricted to most of his music composed between about 1892 to 1903 and to certain specific later compositions strongly resembling those works in style. Some of these Impressionist works would be the opera Pelléas et Mélisande (first performed in 1902), the orchestral piece “Nuages” (“Clouds,” from Nocturnes, completed in 1899), and the piano piece “Voiles” (“Sails,” from Douze Préludes, Book I, 1910). Other composers considered Impressionistic include Maurice Ravel, Frederick Delius, Ottorino Respighi, Karol Szymanowski, and Charles Griffes.

Musical Impressionism is often thought to refer to subtle fragility, amorphous passivity, and vague mood music. A more accurate characterization of Impressionist music would include restraint and understatement, a static quality, and a provocatively colourful effect resulting from composers' fascination with pure sound as a beautiful and mysterious end in itself. Technically, these characteristics often result from a static use of harmony, ambiguous tonality, a lack of sharp formal contrasts and of onward rhythmic drive, and a blurring of the distinction between melody and accompaniment. Although Impressionism has been considered a movement away from the excesses of Romanticism, the sources of many of its characteristics may be found in the works of composers who are also considered to be the Romantic precursors of Expressionism—e.g., Franz Liszt, Richard Wagner, and Aleksandr Scriabin.