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.
I remember the same, was it mythbusters or something?
It’s one of those home experiments that is super easy to do and impress the kids. You just pour a bunch of cereal into a ziplock bag and move a magnet around on the outside until you start to see the little black dust appearing on the magnet.