If you are not too lucky you’ve been at the dentist’s and maybe you already have a ceramic crown with metal in your mouth, or some of them. But hardly you know what happens outside the dentist’s room and how they make these crowns. Now you have a chance to find it out.
These are four perfectly round, concentric circles. Wait no, they aren't. Oh yes, they are. No, they are not. Are they? No. Yes. Would you please stop moving right now? Stupid circles made of stupid squares. [Thanks Karl!]