Abstract: A specimen preparation unit having a plurality of interconnected compartments is automatically loaded onto a centrifuge rotor arm at a first rotor position. Each rotor arm has two indexing means for independently rotating the unit about either or both of two axes orthogonal to each other and to the rotor arm. The orientation of the unit with respect to the centrifugal force vector is changed in a predetermined manner so as to cause fluid flow between desired compartments even under conditions of microgravity. The unit is centrifuged in at least two different orientations with respect to the centrifugal force vector. As the fluids move between compartments, the specimen is prepared. After the multistep preparation process is completed, the unit is rotated to another rotor position at which the prepared specimen and/or the entire unit is removed. The centrifugal processing unit is capable of processing a plurality of specimen preparation unit in the same or a different manner.