 In 2007, David Chipperfield designed an extension, which was then built onto the older building., director of the museum in the 1920s and 1930s, and earlier directors, had made the museum's collection of modern art into one of the leading collections in the world.However, when the National Socialists came to power in Germany in the early 1930s, they instituted a government-wide purge of what they termed "degenerate art", by which they meant abstract, cubist, expressionist, surrealist and impressionist art.