This quilt, which is available with optional blood red thread (if you ask for it as a custom thread color), displays the Heme molecule, which is the active center of hemoglobin in the blood. The function of hemoglobin is to transport oxygen through the bloodstream. A single iron atom, not covalently bonded to anything but held in place by its +2 electric charge, is responsible both for the red color of blood, and its ability to bind oxygen.