From the beginning of the twentieth century, many artists abandon the territory of idealism, reject all traditional forms of representation and deserted institutional places to immerse themselves in the order of things. Reality becomes a primary concern, with the consequent redesign of the "world of art", from the gallery to the museum, from the market to the concept of art itself. Emerging practices and new artistic forms then emerge: art of intervention and engaged art of activist character, art investing urban space or landscape, participative aesthetics or active in the fields of economy, media, or entertainment. The artist becomes an involved social actor, often disruptive. As for the work of art, it adopts a resolutely new, problematic, more than ever in relation to the world as it is. She calls for the enhancement of raw reality, the "context" precisely. The art becomes contextual. It is from this inflection, characteristic of modern and contemporary art, that the author maintains us by delivering the first synthesis on the subject. He favors concrete examples but also the questions that these practices do not fail to raise.