An electronic wedding cake In nanostructures such as quantum dots, spatial confinement forces electrons to assume discrete energy levels. Quantization can also occur in an external magnetic field, where electrons' energies group into so-called Landau levels (LLs). Gutiérrez et al. explored the interplay between these two mechanisms and electronic interactions in a circulator resonator made of graphene. As an external magnetic field was increased, the electron quantum states transformed from atomic-like states to LL-like states. Electronic interactions caused a characteristic wedding cake–like shape of electronic density at high fields. Science , this issue p. 789