The mechanisms that govern the rate at which glasses soften on heating have long been a mystery. The finding that colloids can mimic the full range of glass-softening behaviours offers a fresh take on the problem. For hundreds of years, scientists have wondered how glass-forming liquids solidify without crystallizing as they cool — or indeed without undergoing much change in structure at all. Glass artists take advantage of this continuous rigidification process to create and preserve liquid 'form' and 'action', fascinating onlookers as they turn glowing globs of hot molten glass into elegant shapes.