A recent study led by Javier Abajo from the Institut de Ciencies Fotoniques (ICFO) and Qing Dai from the National Center for Nanoscience and Technology (NCNST) of the Chinese Academy of Sciences (CAS) demonstrated a gate-tunable nanoscale negative refraction of polaritons in the mid-infrared range through a van der Waals heterostructure of graphene and molybdenum trioxide.