A trauma patient is wheeled into the emergency department, her injuries severe, blood pressure dropping. The surgeon calls for blood - O negative, the universal donor type, needed immediately. Within minutes, units arrive from the hospital blood bank. The blood that will save her life was donated by a stranger weeks ago, processed and tested and stored, ready for this moment. A cancer patient receives a platelet transfusion, the treatment that destroyed her bone marrow requiring ongoing blood product support. A newborn with a rare blood condition needs an exchange transfusion.