Why does blood not stick to human skin like a permanent marker, yet stains things like clothes really badly? How does circulation work after an amputation? How many blood types are there? What does A B & O mean? If blood in your veins looks blue, why do we never see blue blood when we get a cut?

... We explain like i'm five!

Thank you to the r/explainlikeimfive community as always and in particular the following users whose questions and comments formed the basis of this discussion: liquidbottle, old_story, uniwersal, turbotitan92, despicablenewb, alloftheabove12, kyylye, somepoet, skillyskally & phage0070

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