Rothko largely abandoned conventional titles in 1947, sometimes resorting to numbers or colors in order to distinguish one work from another. The artist also now resisted explaining the meaning of his work. "Silence is so accurate," he said, fearing that words would only paralyze the viewer's mind and imagination. By 1949 Rothko had introduced a compositional format that he would continue to develop throughout his career. Comprised of several vertically aligned rectangular forms set within a colored field, Rothko's signature, lent itself to a remarkable diversity of appearances. In these works, like No.9 (Dark over Light Earth), 1954, large scale, open structure and thin layers of color combine to convey the impression of a shallow pictorial space. Color, for which Rothko's work is perhaps most celebrated, here attains an unprecedented luminosity.