At some point, everyone learned in school that there are four distinct blood types: A, B, AB and O. Each is further defined by a positive or negative rhesus factor. Which blood type you have is already determined before birth. Above all, it’s important to know your blood type if you need a transfusion because not all blood types are compatible with one another. But did you know that your blood type also has numerous other effects on you? Here are 10 facts about how blood influences your life that you probably weren’t aware of.