Mayonnaise is one of the French 'Mother' sauces, or basic sauces, from where many of the sauces we still use today, come from. Then there are daughter sauces, which have a mayonnaise base which include; tartare, aïoli, Marie rose and Elizabeth. This sauce is made by emulsifying egg yolks with oil. The egg yolks contain lecithin, which is a protein. Normally, if you had a jug of oil and added water, the two ingredients would form different layers. The lecithin is able to combine with water and oil and create a stable sauce. The water in the sauce being lemon juice or vinegar or both. Other 'Mother ' sauces which are emulsified are Hollandaise and Beurre Blanc.