In Persian art of the medieval time, the polygonal sub-grid system, which is based on extensive use of geometric constructions, is the only method for which there is documented proof. Artists and craftsmen used this method widely that exhibited their high skill or collaborations with geometers-throughout the Islamic world. Nevertheless, it would be a great mistake to assume that one, and only one, method was responsible for all the ornamental patterns and tiling designs of Persian art. The modularity approach based on color contrast of cut-tiles may be considered as another possible method used by artisans based on techniques of trial and error.