A flashlight beam in fog breaks into thousands of faint specks. Each speck is light that has bounced off countless water droplets before reaching your eye. To make sense of this mess, physicists construct a special table — the scattering matrix. It records how each incoming ray turns into a set of outgoing ones.

The authors of the new study skipped the fog and used a single glass bead — the simplest possible scatterer. They illuminated it with a laser from various angles and recorded how light emerged in all directions. To do this, they used holography: the laser beam was mixed with a reference beam, and from the interference pattern they reconstructed the full light wave — not just its intensity but also its phase. This allowed them to measure the scattering matrix with precision down to the polarization of light.

After correcting for optical distortions and recalculating angles, the measured matrix matched the theoretical one. This means the method works and can now serve as a benchmark for testing more complex media — for instance, biological tissues, where light scatters off cells and organelles.