A beam of light hits a metal plate with a square structure, and a pattern of tiny magnetic vortices appears on its surface, like ripples on water, but frozen and orderly. These vortices are called skyrmions, and they behave like spinning tops that can rotate in different directions.

If you look at the plate very closely, the vortices line up in one pattern: they look like hedgehogs with spines sticking outward. But step back a bit, and the pattern changes: now the vortices resemble coiled snails. The transition between these two patterns is not smooth but abrupt, like shifting gears in a car.

You can control this switching simply by changing the height at which you observe the surface. This opens the way to devices where information is written not by electric current but by light — fast and without heating.