The Ouzo Effect is the name given to the spontaneous rapid formation of an emulsion - micro and nano-scale oily droplets suspended in water - when (as an example) the alcoholic drink Ouzo is added to water (or vice versa).

'Normal' emulsions require the addition of a 'surfactant' (soap-like) chemical, and agitation, to achieve the emulsion.

The 'Ouzo' type of emulsions are stable - they don't settle out - the droplets stabilizing with an average diameter of around 3 microns

The exact electro-chemical mechanisms which produce the effect are not yet understood.

There are a number of applications of the effect in the manufacture of pseudo-latexes, silicone emulsions, and biodegradable polymeric nanocapsules etc.

See : ChemPhysChem Volume 6, Issue 2 p. 209-216