Emulsions force oil and vinegar to temporarily coexist

These two distinct liquids despise each other on a molecular level and will always attempt to violently separate into distinct layers. To make a stable dressing, you must vigorously whisk them together alongside a chemical mediator, like mustard or egg yolk. This binds the hostile fat and acidic molecules together, forcing them into a thick, delicious truce that defies their natural physical properties.