Laboratory centrifuge. Vials in the four cradles of a laboratory centrifuge. The cradles pivot around their upper ends, swinging outwards as the central rotor rotates. As the samples are spun at high speeds, denser material will settle at the bottom of the vial. Samples used in centrifuges include blood (in the vacutainers, purple caps) and suspensions in liquids. The opposite sides of the centrifuge must be precisely and equally loaded, as shown here. This avoids the machine being damaged by small imbalances of the extreme forces experienced during rotation.