The successful synthesis of a certain cage is determined 16 by whether the building blocks self-sort into the chemist's 17 desired product (generally this is a single species, but could 18 be a targeted mixture). The eventual cage structure has two coordinates of atoms or building blocks in the cage structure, which has been closely linked to regular shapes or polyhedra while rigid building blocks are used. Indeed, under these conditions, building block geometry and stoichiometry can predict topological outcomes, which infer geometrical properties. But researchers are targeting more complex structures (toward improved tunability) through flexible, unsymmetrical, or mixed components. Therefore, the degrees of freedom to be considered will only grow, making the use of existing design rules for cages less viable.