Tailor-made microparticles and nanoparticles are finding increasing use in food products to alter their nutritional characteristics, flavor profile, appearance, rheology, stability, and processability. These particles are often fabricated from food-grade biopolymers, such as proteins and polysaccharides. Food biopolymers display a diverse range of molecular and physicochemical properties (e.g. molecular weight, charge, branching, flexibility, polarity, and solubility) which enables the assembly of colloidal particles that exhibit a broad range of functional attributes. By careful selection of appropriate biopolymers and assembly methods, biopolymer particles can be fabricated with tailored behaviors or features. In this article, we review recent developments in the design and fabrication of functional biopolymer nanoparticles and microparticles, and highlight some of the challenges that will be the focus of future research. Display omitted •Micro- and nanoparticles find increasing application in the food science field.•Particles can be used to optimize nutritional properties, flavor, appearance and processability of food products.•Different biopolymers such as proteins and polysaccharides can be used to produce food-grade micro- and nano-particles.•Particle characteristics determine the functionality and stability of the particles in a food matrix.•Future research on particle design should be directed to the development of quantitative structure–function relationships.