An emulsion is what you get when you put two or more liquids together and the two liquids do not mix. Immiscible liquids do not mix together. For example, if you add oil to water, the oil floats on the surface of the water. And if you shake the two together then leave them to stand, tiny droplets of oil float upwards. These droplets join together until eventually the oil is floating on the water again. To stop the two liquids separating, we need a substance called an emulsifier.