In the culinary world, emulsion refers to the mixing of fat and water. The effect can be permanent or temporary. It’s definitely a science because it defies the general understanding that oil and water do not mix. Under normal circumstances, these two ingredients have a tendency to separate. However, combining certain ingredients together can create an emulsifier, like a glue, so that the water and fat adhere together. Some examples include vinaigrettes, hollandaise sauce, and mayonnaise.