Countercurrent chromatography separates mixtures using two immiscible liquids instead of a solid stationary phase. In an open column, centrifugal or gravitational fields hold one liquid layer in place while the other flows through, partitioning compounds between them. Natural-product chemists prize it for preparative isolation of delicate substances, including tea polyphenols and fruit and vegetable anthocyanins, because the absence of solid adsorbents avoids irreversible binding and breakdown. Recoveries are high, making it ideal for purifying labile pigments and antioxidants. Scale-up from analytical to preparative columns gives manufacturers kilogram quantities of high-purity natural compounds for foods and supplements.