Do you know your ABO's? These letters may spell the difference between life and death if a person needs a transfusion. Use this creative simulation to improve your students' understanding of antigens and antibodies and their role in blood typing and transfusions. No blood, blood products, or simulated blood required. Each student makes their own “blood bag” containing a specific type of paper red blood cell and any accompanying antibodies. Then, they exchange and mix their “blood” with one another. The basic principles of blood transfusion are discovered as students identify the exchanges that will be “rejected” by the human body.Kit includes reproducible student handouts and zipper-type bags for the storage of parts sufficient for 32 students.