It sounds like a party trick: Add water to the clear, licorice-flavored ouzo liquor, and watch it turn cloudy. This "ouzo effect" is an example of an easy way to make highly stable emulsions—or mixtures of liquids that don't like being together, like vinaigrettes—but nobody has yet fully understood how it works. Now, researchers report in ACS Central Science that the secret may lie in the unique structure of the emulsion's droplets.