Originally described by Stang and co-workers, this approach deals with two basic structural requirements; (i) the complementary precursor units must be structurally rigid with predefined bite angles, and (ii) the appropriate stoichiometric ratio of the precursors must be used. The donor building blocks are usually organic/metalloorganic ligands with two or more binding sites possessing angular orientations ranging from 0° to 180°, and the acceptors are metal-containing subunits, usually structurally rigid with fixed pre-defined coordination sites. For example, a tetrahedron can be broken down into four 60° tritopic (blue) and six ditopic (red) 180° subunits, where the tritopic units represent the ligand on the edges, resulting a M4L6 tetrahedron. Conversely, a M6L4 tetrahedron can be generated from linear metal units (ditopic) on the edges and tritopic ligand on the vertices (Figure ).