Blood fractionation

Blood fractionation is the process of fractionating the blood - that is, of separating it into its component parts: erythrocytes (or "red blood cells"), blood plasma, and platelets. The first practical large-scale method of blood fractionation was developed by Edwin J. Cohn during the Second World War. Also known as plasma fractionation or the Cohn method.

the whole blood can be cetrifuged to get a clear suspension of "plasma" in the upper phase, the WBC's in the middle buffy coat and the erythrocytes in the bottom.