Observation of branched flow of light.

When waves propagate through a weak disordered potential with correlation length larger than the wavelength, they form channels (branches) of enhanced intensity that keep dividing as the waves propagate. This fundamental wave phenomenon is known as branched flow. It was first observed for electrons and for microwave cavities, and it is generally expected for waves with vastly different wavelengths, for example, branched flow has been suggested as a focusing mechanism for ocean waves, and was suggested to occur also in sound waves and ultrarelativistic electrons in graphene.