Blood for transfusion therapy is collected through either whole blood donation or by automated apheresis. Whole blood donation involves the collection of a unit of blood from a donor, which can then be separated into components (red cells, plasma, and platelets). Apheresis is a technique in which the donor is connected to a machine that separates and selectively collects a specific component of the blood—such as plasma, platelets, or red cells—while the remaining blood elements are then returned to the donor. Other components such as granulocytes and stem cells are also collected by apheresis. Blood donors receive detailed information about the collection process and the tests that will be conducted. After providing informed consent, eligible donors proceed with the donation. The collected blood is then sent to a manufacturing laboratory for processing into various blood products. Rigorous testing ensures the safety of the blood products before they are made available for transfusion. Testing for red cell alloantibodies, ABO type, and infectious diseases is performed; other testing such as HLA and neutrophil antibodies may be added. Units are stored at determined conditions and transfused as appropriate. Modifications such as leukoreduction, irradiation, and washing are performed routinely or according to clinical need.