The structures and composition of crab carapaces are of interest to biomimetic designers and materials scientists as they are hierarchically optimised to dissipate fracture energies through molecular to macroscopic length scales. At each length scale, mechanical energy is absorbed and redirected, circumventing thus catastrophic fracture through the carapace cross-section on impact. The objective of this section is to elucidate the structural, chemical and compositional makeup of crab carapaces, to provide links between their architectures and mechanical properties, and to discuss highlight papers where attempts have been made to mimic the structure-property characteristics of crab carapaces in modern engineering composites.