Blood centrifuge. Gloved hand loading a blood sample in a microtube into a centrifuge. Centrifuges separate out the blood cells from the fluid (serum) by spinning the sample at high speed. The force of spinning pushes the densest matter to the very bottom of the microtube. Centrifuging is carried out when only one of the components of blood needs to be tested. Rubber gloves help to maintain sterile conditions.