The egg yolk is the yellow part of an egg, found at the center and surrounded by the egg white. It serves as a source of nutrition for the developing embryo in fertilized eggs. Rich in vitamins, minerals, and fats, the yolk contains essential nutrients like vitamin D, vitamin B12, and choline. In cooking, the egg yolk is often used for its rich flavor and creamy texture. It is a key ingredient in many recipes, including mayonnaise, custards, and sauces. The yolk can also be separated from the white for various culinary techniques, such as making meringues or enriching doughs.