Nested spaces. Perhaps the most important point involves the implications of the modular structure theorem. The topologies that emerge from the formalism are contain simpler topologies but are themselves nested within more complex topologies. The "shape of chemical space" that emerges is made up of common forms that map across and through its grand structure. Perhaps should not be a surprise as it offers an explanation for why, in chemical synthesis, a given set of reaction conditions acting upon vastly different substrates will generally lead to predictable products; why reactions can be classified into general types; why we see the same geometric forms again and again.