Unlike the concrete and steel of buildings and bridges, most mechanical elements of biological tells are soft, in that their shape is su bject to significant thermal fluctuations. For instance, the compression resistance of a protein network may be orders of magnitude less than Chat of the air we breathe. How do these materials, selected by evolution, act cooperatively to create a functloning cell? Aimed atsenior undergraduates and graduate students in science and, biomédical engineering, this text explores the architecture of the cell's envelope and' internat scaffolding, and the properties of its sort components. The book first discusses the properties of individual flexible polymers, networks and membranes, and then considers simple composite assemblages such as bacteria and synthetic ceps. The analysis is performed within a consistent theoretical framework, aithough readers can;.navigate from the introductory material to resuits and biological applications without working through the intervening mathematics. This approach, together with a glossary of terms and appendices providing quick introductions to chemical nomenclature, tell structure, statistical mechanics and elasticitytheory, makes the text suitable for readers from a varlety of subject backgrounds. Further applications and extensions are handled through problem sets at the end of each chapter and supplementary material available on the internet.