A second characteristic of attractor dynamics is resilience to perturbations, i.e. readily undergoing returns to the steady state after being diverted by intrinsic or extrinsic agents . This attribute has been evoked by studies of biological attractors, where a cellular system in steady state is perturbed by controlled stimuli, and subsequently relaxes back to the attractor . As shown in Figure , compositional perturbations induced by imperfect assembly fission are followed by a return to the attractor composition. The important conclusion of these observations is that compositions that allow assembly self-reproduction are dynamic attractors .