NCTR scientist prepping centrifuge. A centrifuge is a piece of laboratory equipment. The rotating unit, called the rotor, has fixed holes drilled at an angle (to the vertical). Test tubes are placed in these slots and the motor is spun. As the centrifugal force is in the horizontal plane and the tubes are fixed at an angle, the particles have to travel only a little distance before they hit the wall and drop down to the bottom. The National Center for Toxicological Research (NCTR) is FDA's internationally recognized research center. The unique scientific research expertise of NCTR is critical in supporting FDA product centers and their regulatory science roles. NCTR, in partnership with researchers from government, academia, and industry, develops, refines, and applies current and emerging technologies to improve safety evaluations of FDA-regulated products.