Pop art emerged in the 1950s and celebrated commonplace objects and popular culture. Key artists included Richard Hamilton and Edouardo Paolozzi in Britain as well as Andy Warhol in the US. In Germany, Capitalist Realism had a similar focus on consumer culture and mass media imagery, led by Sigmar Polke. France saw the Nouveau Réalisme movement which directly incorporated mass culture, championed by artists like Yves Klein. Op art used optical illusions to confuse the eye, exemplified by Victor Vasarely's works. Viennese Actionism featured extreme performances using organic materials. Arte Povera criticized modernity and technology through works incorporating everyday items. Neo-Expressionism revived painting