Emulsifiers are substances that help keep the ingredients of a product blended together, even when they would normally separate. This creates a smooth, stable mixture that won't separate over time. A popular example of an emulsifier is lecithin, which is a type of fat derived from egg yolks and soybeans. It's commonly used in food products, such as margarine and mayonnaise, to keep the oil and water parts of the product from separating.