Abstract: Differential geometry involves the study of smooth manifolds, which is a mathematical formulation of shapes we can do calculus on. To measure lengths, angles, etc we may endow such shapes with the extra structure of a Riemannian metric, and we often understand a Riemannian metric through its curvature. In this easy going talk we’ll lightly introduce some of these notions culminating in Gauss’s theorem Egregium — that literally means remarkable theorem — which tells us why maps of the globe can never be quite right, up to scale. Perhaps more importantly, it also tells us how to eat pizza correctly. Contrary to how it might sound no great prerequisites are assumed; it would be nice (but not essential) if you’ve seen what a matrix is and know about the determinant.