For me it is the fact that our blood contains iron. I earlier used to believe the word stood for some ‘organic element’ since I couldn’t accept we had metal flowing through our supposed carbon-based bodies, till I realized that is where the taste and smell of blood comes from.
Similar metal in the human body one, Vitamin B12 has cobalt in it. Absolutely wild. I guess that’s not really commonly known but it’s still worth mentioning
and vitamin D has mithril in it
vitamin D warf