Blood comes in 4 majors types. These are A, B, O, and AB. These types of blood are inherited by parents. Alleles in a parent’s genetic makeup determines what type of blood a child has. The blood types are composed of the red blood type cell, the antibodies in the plasma, and the antigens in the red blood cell. An antigen is a substance that causes an immune system to produce antibodies. An Antibody is used to identify and neutralize bacteria and virus cells. Antibodies are Y shaped. Group A type blood has Anti- B antibodies in the plasma, and A antigens. Group B type blood has Anti-A antibodies and B antigens. Group AB has no antibodies and has A and B antigens. Group O has Anti A and Anti B antibodies and zero antigens. These parts of the blood determine how compatible blood is with other blood. This can be useful in transfusions, and organ donations. The positive and the negative associated with blood indicates if the Rhesus comes from an antigen found in the red blood cell. By keeping blood at a certain temperature, and storing them in blood banks, blood chillers are an important part of saving people’s lives.