Fibrillar structure and elasticity of hydrating collagen: A quantitative multiscale approach

► General rules for hydration-induced collagen swelling and softening are identified. ► Fibrillar volume swelling is quantified from X-ray diffraction data. ► Fibrillar elasticity is quantified from Brillouin light scattering. ► Extrafibrillar space grows proportional to fibril swelling. ► Transversely isotropic elasticity of molecular collagen is hydration-independent.