At the submicron scale, food biopolymer networks can be visualized by a wide array of microscopic techniques, but these methods are mostly invasive and require careful image analysis in order to quantify network features. ‘Nanoparticle diffusometry’ provides a non-invasive alternative to infer quantitative submicron structural information about biopolymer networks. In this approach, spectroscopy-based methods are used to monitor hindered diffusion of nanoparticles due to network obstructions. Both rigid-spherical and flexible nanoparticles can be used and models are available to derive structural network parameters. A range of applications to polysaccharide and protein sols and gels has been described. The approach offers opportunities to assess (sub-)micron scale network heterogeneity and changes in sub-micron structure under dynamical conditions such as shear or aging.