A split image shows Allen Ginsberg in 1953 and 1967. Allen Ginsberg LLC/Corbis | The National Portrait Gallery hide caption

itoggle caption Allen Ginsberg LLC/Corbis | The National Portrait Gallery

Marcel Duchamp's Cubist-inspired Nude Descending a Staircase was famously described by one critic as "an explosion in a shingle factory." Philadelphia Museum of Art/Copyright succession Marcel Duchamp / ADAGP, Paris / Artists Rights Society (ARS), New York 2013 hide caption

itoggle caption Philadelphia Museum of Art/Copyright succession Marcel Duchamp / ADAGP, Paris / Artists Rights Society (ARS), New York 2013

Very little is known about Girl With a Pearl Earring, which is often referred to as the Dutch Mona Lisa. Superstock/The Art Archive hide caption

itoggle caption Superstock/The Art Archive

Grapes, a spiky cluster of wooden stools from the Qing Dynasty (1644-1911), is part of Ai Weiwei's repurposed furniture series. Cathy Carver/Courtesy Hirshhorn Museum hide caption

itoggle caption Cathy Carver/Courtesy Hirshhorn Museum

Edward Hopper is well-known in the U.S. for paintings such as Nighthawks (1942)pensive, lonely portraits of people sitting together yet alone. He was less well-known in France, but an exhibit of his work at the Grand Palais has drawn impressive crowds. The Art Institute of Chicago, Friends of American Art Collection/Courtesy of the Art Institute of Chicago hide caption

itoggle caption The Art Institute of Chicago, Friends of American Art Collection/Courtesy of the Art Institute of Chicago