These four droplets consist mixtures of oil, alcohol and water. Astonishingly, with time the oil and water form multiple shells composed of alternating oil/water layers by phase separation. This happens because the solvent that initially mixes oil and water escapes the droplet to the surrounding water. Pay attention to droplets (c) and (d): At 10 seconds they complete the first phase separation, but this looks clearly different for droplet (c) compared to droplet (d). The reason is: droplet (c) phase separates by nucleation, droplet (d) by spinodal decomposition.