There are numerous ways of preparing PRP, but, in essence, a volume of blood, ranging from 10–60 ml, depending on the process being used, is drawn from the patient. A centrifugation process separates the red blood cells, white blood cells and platelets into a number of different layers. One is rich in red blood cells, another layer (the buffy coat) may be rich in platelets and white cells, and another layer will contain platelet-poor plasma.