" There is nothing like it. It is stardust and the sea. The iron in our blood comes from the death of supernovas, like all iron on our planet.5 This bright red liquid—brighter in the arteries, when it is transporting oxygen around the body from the heart, duller in the veins, when it is not—contains salt and water, like the sea we possibly came from. "

― Rose George , Nine Pints: A Journey Through the Money, Medicine, and Mysteries of Blood