The process used to separate or concentrate materials that are suspended in a liquid is termed as centrifugation. Centrifugation works on the principle of gravity settling, that is particles of different masses settle at different rates due to gravity. This principle of differential settling is aided by a centrifugal force which is applied to the system. Centrifugal force is that force generated when an object rotates in a circular or elliptical motion. For example when a yo-yo is rotated the force generated on the string to keep the yo-yo in motion is centrifugal force. A device that uses the above principle is termed as a centrifuge.

A centrifuge is the device that is used in scientific and technical application which requires the materials to be spun at high rotational speeds and high centrifugal force. The centrifugal force (usually expressed as xg) generated is proportional to the rotation of the rotor (in rpm) and also the distance between the rotor centre and the centrifuge tube. Multiple rotors sizes give flexibility to the conditions. A special graph termed as nomo-graph is drawn which relates the rotor speed (rpm) versus the centrifugal force (xg). This graph helps in selecting proper centrifuging conditions for the different sizes of rotor it accepts.

The material to be spun is kept in containers known as centrifuge - tubes which in turn are kept in rotors. The rotor is made of a dense metal which serves two purposes: one is to dissipate heat quickly and the other is to generate high momentum.

The centrifuge usually works in vacuum so as to reduce frictional forces due to spinning. Rotors are usually stored under refrigeration so as to keep them as near to the operating temperature as possible.

Centrifuges come in different sizes and shapes, the rotors also vary depending on the centrifuging conditions required. ‘xg’ is the universal and transferable unit of centrifugation.