The sketches for the stained-glass windows by Marc Chagall at the Centre Pompidou-Metz reveal his long working process. A lead path shapes the network that the pieces of glass would form. The number of the color used is written on each part. Chagall worked by superimposing several layers of colors and adding acid to alter them before firing. He later added tiny gray additions to create a reflection. The stained-glass windows resulted from his imagination combined with the know-how of master glassmakers Brigitte Simon and Charles Marq.