Living cells are constantly exposed to a wide variety of mechanical stresses: heart and lungs must withstand expansion and contraction; our skin must be resistant to tearing whilst retaining elasticity; immune cells are squashy so they can move through the body. ‚Intermediate filaments‘ (special protein structures), play an important role here. Researchers have now measured what determines the properties of individual filaments, and which features only occur through the interaction of filaments in networks.