Oil and vinegar salad dressing. Layers of oil (top, yellow) and vinegar (bottom, orange) in a jar, ready to be used as a salad dressing. Oil and vinegar are immiscible liquids. When shaken together they form an emulsion, a mixture of small droplets. When left for a while, the two liquids separate into different layers, as seen here. For the emulsion, see image H110/4607.