The Building Blocks of Life Biological organisms are often limited in the resources that they can use to make structural materials. Primary building blocks may be weak or brittle materials, such as minerals and biopolymers, and processing conditions by default have to be mild. Despite this, a wide range of strong and tough structures exist, including shells, bones, quills, and fibers. Meyers et al. (p. 773 ) review a wide range of materials and architectures used in nature to make strong and tough materials and show how many of the design principles have also been used or are being considered for manmade materials and structures.