Heinz Mack is best known for his sculptures and reliefs. In the postwar years, however, Mack created a groundbreaking series of paintings that were built on radical reductions of color and a concentration on light and rhythm. The paintings of that period—now known as the ZERO years, gave way later in the 1950s to his Dynamic Structures, works in which a painting of light is set in contrast with traditional approaches to color and structure replaces composition. This catalogue raisonné offers an unprecedented look at Mack's early work, showing it to be indispensable to an understanding of his whole career.