Pieced quilts always have the potential to be optically complex: placing hundreds or thousands of fabric patches together naturally produces visual intricacies. But a few design elements can transform pieced quilts into compositions with added qualities of optical illusion. In these pieces from Abstract Design in American Quilts, tessellation—repeating geometric shapes without gaps or overlaps—and value contrast—differences between lights and darks—produce these phenomena. Tessellation in American pieced quilts often takes the form of patterns like Thousand Pyramids (repeating triangles) and Tumbling Blocks (repeating rhombi). Alternations and differences help the eye make sense of an overall pattern. But in tessellation, because the shapes fit neatly together, the eye keeps moving across the surface, with no obvious place to rest. Value contrasts also can unsettle the eye, especially when they create figure/ground reversals, in which the foreground and background seem to switch back and forth, with the light areas in one instance being perceived as the foreground then switching to the background, and vice versa in the dark areas.