Under the right conditions, interactions between electrons can cause magic-angle graphene to enter exotic collective states, including superconducting and insulating phases. Magic-angle graphene offers another route. Their experimental device consisted of magic-angle graphene sandwiched between layers of hexagonal boron nitride and configured as a field-effect transistor. A graphite back gate allowed them to precisely control the number of charge carriers and tune the graphene into its correlated insulating state. The effect currently requires ultra-low temperatures, and the unusually strong response depends upon generating high-quality magic-angle graphene structures.