Cosmetics are items or substances designed to improve or modify the look of the hair, body, or face. They are typically applied to the skin or hair and serve a range of purposes, such as beautifying, cleansing, moisturizing, or protecting the skin. The cosmetics industry has recently tried to please consumers with various innovative products to meet their demands and needs. Cosmetics can be broadly classified into several types: makeup, skincare, haircare, fragrances, and personal care products. Specifically, skincare products attract the most attention in the cosmetic industry since they focus on maintaining and improving the well-being and aesthetics of the skin. Their range encompasses products such as those for cleansing, toning, moisturizing, nourishing, exfoliating, and sun protection. Therefore, this chapter describes the basic theory and formula of skincare products that can help readers quickly discover the essential cosmetic industry.