Nature: A crystal can grow only if all of its atomic or molecular building blocks fit into the periodic lattice. This is true even for colloidal crystals, which form through the ordered self-assembly of micrometer-sized particles. The requirement for periodicity puts stringent constraints on the variation in the size of particles that can be incorporated into a given colloidal crystalline lattice.But reporting in Angewandte Chemie, Ashlee St. John Iyer and L. Andrew Lyon show that crystals made of microgel particles are much more tolerant of particle size variations than was expected. This surprising feature might have practical implications for the design of ordered colloidal materials. Related LinkLyon Research GroupPayne Laboratory