In nacre, layer lattices of inorganic calcium carbonate alternate with layers of organic material. Chitin, collagen and various proteins ensure that the calcium carbonate grows in these defined layers. What role the proteins play during growth had not previously been explained, but the assumption was that several proteins acted together to control the structure of the calcium carbonate lattice as well as themselves forming part of the nacreous layers. However, now researchers have now shown that the crystal lattice of calcium carbonate can be altered using just a single protein species.