Shampoos are the most important hair care products in terms of volume. More than 4 billion bottles, manufactured and marketed by several hundred companies, are sold annually around the world. A shampoo is generally presented as a liquid, gel, or cream. The primary function of a shampoo is to clean the hair and the scalp. The primary function of shampoos rests on the use of synthetic detergents. Careful selection is essential because they set the washing power and for a large part the quality of the foam, as well as the level of eye and skin tolerance of the composition. The “secondary” functions of hair conditioning are provided nowadays in high performance shampoos by two major types of ingredients used alone or combined, that is, cationic polyelectrolytes and silicone oils. Shampoos can also contain thickening polymers such as cross-linked poly-acrylic acids or certain polysaccharides. Finally, shampoos also contain perfume and agents for bacteriological protection.