H. -S. Sim

A stone falls into water, and ripples spread outward. In the quantum world, a magnetic impurity (that pebble) in a metal perturbs the surrounding electrons, and they form a special cloud around it. This is called the Kondo cloud. Like ripples on water in the dark, it long remained elusive.

The quantum world is full of surprises: swap two electrons, and their combined wavefunction just changes sign; swap two photons, and nothing happens at all. But there are particles that behave very differently when exchanged, as if they remember being swapped. These particles are called anyons, and they can only exist in a two-dimensional world.