Biomineralization produces a wide range of functional crystals of unusual morphologies, often appearing to be multi-domain; they mainly consist of polymorphs of calcium carbonate. For example, the hammer-shaped building units of coccoliths, sponge-like morphologies, and the curved surfaces of sea-urchin skeletal elements are all single crystals. Only a few clear examples of organic crystals and metal-organic frameworks (MOFs) are known to be single crystals while exhibiting a multidomain appearance. Recently, Oki et al. have shown that concave polyhedral single crystals form on surfaces from chiral organic molecules. These complex molecular crystals are formed in the absence of additives.