Abstract: A system of form bodies for use as a toy building blocks, decorative objects, in particular for display use, furniture structures, sculptural building components etc., wherein each form body has the shape of a polyhedron, in which polygonal side faces with each other form polyhedral outward extending protuberances and/or polyhedral inward extending notches for the assembling of differently shaped bodies into spatial structures. In a first group of form bodies each form body is shaped on the basis of a cube and the protuberances and/or notches of the form body are shaped on the basis of a subbody of a cuve and with a shape like a pyramid with a square base, two of the side faces being perpendicular to the base at adajcent sides thereof and each of them has the form of an isosceles right triangle.