798Countercurrent chromatography (CCC) is a liquid–liquid partition chromatography technique that operates without requiring a solid support (Berthod, 2002; Conway, 1992; Foucault, 1994; Ito, 1981a; 1988a; 1995; 1996a; 2000a; 2001a; Ito and Bowman, 1970a, b; Ito and Menet, 1999). The method has evolved from a unique centrifuge device called the coil planet centrifuge (Ito, 1969; Ito et al., 1966a, b; Ito, 1969), which subjects coiled tubes to a planetary motion (i.e., the coil undergoes slow rotation about its own axis along with high-speed rotation around the centrifuge axis). This original coil planet centrifuge was constructed in 1965, when it was aimed at the separation of lymphocytes (Ito et al., 1966b). When the coiled column was filled with nearly equal volumes of two mutually immiscible solvents, one on one side and the other on the opposite side, the planetary motion produced countercurrents of the two phases, which are finally distributed as alternating segments along the coil. When a sample was introduced at the original interface of the two phases, the device separated the solutes according to their partition coefficients, analogously to the countercurrent distribution method (Craig, 1962) but in a continuous fashion (Ito et al., 1969). This success encouraged us to develop a flow-through mechanism so as to perform continuous elution as in liquid chromatography.