The cells that make up our bodies are constantly exposed to a wide variety of mechanical stresses. For example, the heart and lungs have to withstand lifelong expansion and contraction, our skin has to be as resistant to tearing as possible whilst retaining its elasticity, and immune cells are very squashy so that they can move through the body. Special protein structures, known as "intermediate filaments", play an important role in these characteristics. Researchers at Göttingen University have now succeeded for the first time in precisely measuring which physical effects determine the properties of the individual filaments, and which specific features only occur through the interaction of many filaments in networks. The results were published in PNAS.