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In TLC, a sample travels across a plate coated with a stationary phase, commonly silica gel or alumina, as a mobile-phase solvent moves through the layer. Compounds migrate at different rates according to their interactions with both phases; on polar silica, polar analytes are generally retained longer than non-polar analytes. The Rf value relates a compound’s migration distance to that of the solvent front and is characteristic only under fixed conditions. After development, separated components can be visualized using methods such as UV light, iodine vapor, or chemical sprays. TLC supports pharmaceutical identity and purity checks and phytochemical profiling. Its practical strengths include parallel analysis of multiple samples and low solvent use, while lower plate efficiency than HPLC is among its limitations.