Nineteen-year-old expert skier Janne van Enckevort was told that
this cap would harden when his head struck the ice. To make sure, he removed the spongy pads lining the hat, crumpled them into a ball, and then smashed them against the floor. The ball stiffened upon impact, then quickly softened again.

The protective pads morph because they are made of a material called d3o. Engineered by a British company of the same name, d3o is an elastic polymer that tenses in response to quick movements.