That would be a centrifuge.
RBC,WBC,Plasma
They separate it through a machine
A centrifuge is used to separate donated whole blood into components. An Apheresis machine is used to collect blood components directly from a donor, specifically red cells, platelets, granulocytes, peripheral hematopoietic stem cells and/or plasma.
A serum or plasma sample is typically used to test cholesterol levels. The sample is collected in a tube with no anticoagulant or a tube containing a gel separator to separate the serum or plasma from the cellular components after centrifugation.
The centrifuge separates the plasma from the platelets.
A complete blood count (CBC) is typically performed on whole blood, which includes plasma and cellular components. Serum is the liquid component of blood that is collected after the blood has clotted and the cellular components have been removed. So, a CBC is not performed on serum specifically; it is typically performed on whole blood samples.
Basic breakdown for use in transfusion is red cells, plasma, and platelets...however plasma is not a cellular component. Three cellular components may be red cells, white cells, and platelets. Maybe if you could elaborate on the question, it could be better answered.
Most of the time when you get your blood drawn you will notice they do so by filling up a small vial or sometimes a couple. This vial is put into a centrifuge (a machine that spins the vials very fast) to separate three main components in ones blood. Platelets, red/white blood cells, and plasma separate in the centrifuge and all can be extracted purely. A crude example of a centrifuge would be your washing machine on the spin cycle pulling the water out of your clothes. Imagine this on a smaller scale with a vial of blood. The force causes the plasma to separate.
Blood begins to separate into layers due to its different components having different densities. This can occur during the process of centrifugation, where the heavier components like red blood cells settle at the bottom, while lighter components like plasma rise to the top.
Blood can be separated by centrifugation into its components: plasma, which is the liquid part, and cellular components such as red blood cells, white blood cells, and platelets. Another method is using a process called density gradient centrifugation, where a density gradient medium separates blood components based on their differing densities.
You use a centrifuge. This is a machine which spins the sample of blood round. This causes the different substances to separate. Hence, the plasma will separate from the blood cells (which are heavier).
Plasma typically remains thick and does not separate easily during centrifugation when it has a high level of proteins or lipids. These molecules increase the viscosity of the plasma, preventing the components from separating as quickly as they would in normal plasma. This can be seen in conditions like hyperlipidemia or hyperproteinemia.