 In Paris Cousin continued his career as a glass-painter, and created his best-known work, the windows of the Sainte-Chapelle in Vincennes.He subsequently devoted himself to painting in oil, and has been claimed as the first Frenchman to use that new medium.Pictures attributed to him, all of much merit, are found in several of the large European collections, but, excepting "The Last Judgment", none is known to be authentic.