Researchers have developed a way to visualise boron nitride layers that are one atom thick. These ultrathin sheets are typically almost impossible to detect with standard optical microscopes.

The team used nonlinear microscopy with infrared light so that monolayers of hexagonal boron nitride (hBN) light up brightly. Their approach resonantly drives a lattice vibration in hBN, producing a strong signal that not only makes the material visible but also reveals its crystal orientation.