In this work "Vilma" Vasarely created a grid of geometric-abstract forms in bright colors which evokes the impression of a spatial construction. A plastic hemisphere seems to extend into the surrounding space. This way the artist plays with the observer's perception. Even though the observer is well aware of the fact that it is a two-dimensional picture, it can only be perceived three-dimensionally. The illusion of a permanently changing spatial reality adds to the delusion. In his pictures Vasarely negated a universal truth of perception and made major contributions to the formation of Op-Art, of which he was the main representative. [EL]