Biological materials are bottom-up designed systems formed from billions of years of natural evolution. In the long course of Darwinian competition for survival, nature has evolved a huge variety of hierarchical and multifunctional systems from nucleic acids, proteins, cells, tissues, organs, organisms, animal communities to ecological s- tems. Multilevel hierarchy a rule of nature. The complexities of biology provide an opportunity to study the basic principles of hierarchical and multifunctional s- tems design, a subject of potential interest not only to biomedical and life sciences, but also to nanosciences and nanotechnology. Systematic studies of how hierarchical structures in biology are related to their functions and properties can lead to better understanding of the effects of aging, diseases and drugs on tissues and organs, and may help developing a scienti?c basis for tissue engineering to improve the standard of living. At the same time, such studies may also provide guidance on the dev- opment of novel nanostructured hierarchical materials via a bottom-up approach, i. e. by tailor-designing materials from atomic scale and up. Currently we barely have any theoretical basis on how to design a hierarchical material to achieve a part- ular set of macroscopic properties. The new effort aiming to understand the re- tionships between hierarchical structures in biology and their mechanical as well as other functions and properties may provide challenging and rewarding opportunities for mechanics in the 21st century.