Particles on a flat surface usually pack into a simple triangular lattice. How does this change if curvature is switched on? The minimum energy configuration for repulsively interacting particles on curved surfaces is a challenging problem with applications to mathematical physics, computer science and a variety of biological, chemical and condensed matter systems. I will discuss the universal proliferation of novel defect arrays (“scars”) in the ground state of such spherical crystals for sufficiently large systems, including experimental results for self-assembled spherical colloidal crystals.