After the Second World War the West was living a consumer age of strange new intensity: the supermarket, the television commercial, the comic strip, the glossy magazine, Coca-Cola, Hollywood. In London a group of young artists, architects and critics — the Independent Group — began to treat that world not as something art escaped from but as its raw material. For the catalogue of the 1956 exhibition "This Is Tomorrow", Richard Hamilton made a small collage titled "Just What Is It That Makes Today's Homes So Different, So Appealing?" — a bodybuilder holding a giant lollipop labelled "POP", standing among household goods cut from catalogues. For most critics this image is Pop Art's birth certificate.

In the early 1960s the idea exploded on the other side of the Atlantic. In New York, Andy Warhol painted the Campbell's soup cans one by one in 1962; the series of thirty-two canvases moved the supermarket shelf into the museum. In the same years Roy Lichtenstein enlarged frames from romance and war comics by hand, transferring the Ben-Day printer's dots onto canvas; Claes Oldenburg turned everyday objects into vast soft sculptures; James Rosenquist made collages the size of billboards. In Britain Peter Blake and David Hockney followed, in Germany Gerhard Richter and Sigmar Polke.

Pop Art was not a style but a stance: the hierarchy between "high" art and popular culture was refused. Against the grand, inward, heroic canvas of Abstract Expressionism, Pop was cool, ironic, flat — but its flatness was a kind of exposure: the flatness of the consumer society itself. The question of whom art is for was reopened, too: the museum-goer, the collector, the mass? Warhol's Factory pushed that question to factory-scale production.

Its inheritance reaches straight into the twenty-first century. Street art, designer toys, artist–brand collaborations, the digital meme, Banksy, Murakami, Koons — all live inside the frame Pop Art opened. Since the consumer age entered the gallery, art has shared the same ground as the consumer age; there is no longer a before to that line.