Leon Battista Alberti's 1435 treatise De pictura influenced generations of painters by suggesting that a painting should be approached as an open window. By the twentieth century, the window had transformed into a motif that would test the limits of painting. With his 1920 "Fresh Widow"--a replica of a French window with panes covered in black leather--Marcel Duchamp postulated a farewell to illusionist painting. This publication presents the development of window painting by artists such as Robert Delaunay, Henri Matisse, Marcel Duchamp, Ren Magritte, Ellsworth Kelly, Eva Hesse, Gerhard Richter and many others.