Field-flow fractionation (FFF) is a separation technique used to analyze particles, macromolecules, and colloids in a fluid. It operates by applying a field, such as a gravitational or electric field, to a sample as it flows through a channel. This causes different components to migrate at varying rates, allowing for their separation based on size, shape, or density. FFF is particularly useful in fields like biotechnology, environmental science, and materials science. It can effectively separate complex mixtures without the need for stationary phases, making it a versatile tool for researchers studying nanoparticles, proteins, and other biomolecules.