Getting Packed If one neglects the role of specific interactions, the packing of similar-shaped objects will depend only on the particular shape of the object. Damasceno et al. (p. 453 ; see the Perspective by de Graaf and Manna ) present computer simulations of the behavior of different types of polyhedra with simple and complex shapes that are packed under thermal equilibrium into various structures, from crystals to amorphous materials through liquid crystals. Despite the wide variety of starting shapes, the packing behavior could be quantitatively described using just two criteria; one for the particle shape as a function of its volume and surface area, and one for the number of nearest neighbors.