When the 47-year-old Piet Mondrian left the Netherlands for unfettered Paris for the second and last time in 1919, he set about at once to make his studio a nurturing environment for paintings he had in mind that would increasingly express the principles of neoplasticism about which he had been writing for two years. To hide the studio's structural flaws quickly and inexpensively, he tacked up large rectangular placards, each in a single color or neutral hue. Smaller colored paper squares and rectangles, composed together, accented the walls. Then came an intense period of painting. Again he addressed the walls, repositioning the colored cutouts, adding to their number, altering the dynamics of color and space, producing new tensions and equilibrium. Before long, he had established a creative schedule in which a period of painting took turns with a period of experimentally regrouping the smaller papers on the walls, a process that directly fed the next period of painting. It was a pattern he followed for the rest of his life, through wartime moves from Paris to London's Hampstead in 1938 and 1940, across the Atlantic to Manhattan.  At the age of 71 in the fall of 1943, Mondrian moved into his second and final Manhattan studio at 15 East 59th Street, and set about to recreate the environment he had learned over the years was most congenial to his modest way of life and most stimulating to his art. He painted the high walls the same off-white he used on his easel and on the seats, tables and storage cases he designed and fashioned meticulously from discarded orange and apple-crates. He glossed the top of a white metal stool in the same brilliant primary red he applied to the cardboard sheath he made for the radio-phonograph that spilled forth his beloved jazz from well-traveled records. Visitors to this last studio seldom saw more than one or two new canvases, but found, often to their astonishment, that eight large compositions of colored bits of paper he had tacked and re-tacked to the walls in ever-changing relationships constituted together an environment that, paradoxically and simultaneously, was both kinetic and serene, stimulating and restful. It was the best space, Mondrian said, that he had inhabited. He was there for only a few months, as he died in February 1944.  After his death, Mondrian's friend and sponsor in Manhattan, artist Harry Holtzman, and another painter friend, Fritz Glarner, carefully documented the studio on film and in still photographs before opening it to the public for a six-week exhibition. Before dismantling the studio, Holtzman (who was also Mondrian's heir) traced the wall compositions precisely, prepared exact portable facsimiles of the space each had occupied, and affixed to each the original surviving cut-out components. These portable Mondrian compositions have become known as "The Wall Works". Since Mondrian's death, they have been exhibited twice at Manhattan's Museum of Modern Art (1983 and 1995-96), once in SoHo at the Carpenter + Hochman Gallery (1984), once each at the Galerie Tokoro in Tokyo, Japan (1993), the XXII Biennial of Sao Paulo (1994), the University of Michigan (1995), and - the first time shown in Europe - at the Akademie der Kunste (Academy of The Arts), in Berlin (22 February - 22 April 2007).

Answer this question "What is Wall Works ?" by extracting the answer from the text above.
portable Mondrian compositions have become known as "The Wall Works".