Over hundreds of millions of years of evolution, nature has produced a myriad of biological materials that serve either as skeletons or as defensive or offensive weapons. Although these natural structural materials are derived from relatively sterile natural components, such as fragile minerals and ductile biopolymers, they often exhibit extraordinary mechanical properties due to their highly ordered hierarchical structures and sophisticated interfacial design. Therefore, they are always a research subject for scientists aiming to create advanced artificial structural materials.