Familiar materials will act differently at the smallest scales. Notably, diamonds—typically hard and brittle—grow strangely soft at the nanoscale. After years of not quite understanding why, a team of physicists finally managed to decode this behavior. Using a custom-built electron microscope, researchers found that tiny diamonds had a relatively weak chemical bond between their surface layer and their core. Placing nanodiamonds under pressure concentrates the strain at an intermediate region between the diamond’s surface and the core. As a result, the tiny diamond doesn’t fracture but instead reacts like a flexible material, “enabling elasticity that is almost impossible in bulk diamond,” the researchers reported in a recent Physical Review X paper on the findings.…