If you look at the back of any cosmetic product, you will see a long list of ingredients that it contains, all of which have a specific function to ensure that the product is safe and effective. Previous chapters have looked at some of the different types of ingredients that are used in cosmetic products, such as emollients, rheology modifiers and fragrances. This chapter covers a wide range of active ingredients and product types, demonstrating how specific ingredients work in your products and why they are used. The chapter takes a look both at ingredients that are widely used in products to deliver ‘everyday’ functions, such as antioxidants and preservatives, and at some of the industry's ‘special’ palette of active ingredients, such as peptides and vitamins – these are the ingredients that brands like to shout about on the packaging. Although this chapter looks at just a few of the active ingredients typically used (those more commonly found in skincare products), every ingredient used in a cosmetic formulation is added for a specific function. You might want to peruse the ingredient list on some of the products you have at home and compare which ingredients are common across a number of products. Even water is included for a reason! (See Box 8.1).