fuckyeahfluiddynamics:

The immiscibility of oil and water creates a multitude of bubbles of all sizes. A lack of miscibility occurs when the forces between like molecules are very strong for two liquids—essentially the oil molecules and the water molecules are so much more strongly attracted to themselves than they are to one another that they cannot mix. Surface tension—another expression of molecular forces—pulls the oil into droplets that float in the water and refract the light in such lovely ways. (Photo credit: Vendula Adriana Kaprálová Hauznerová; via thinxblog)