Serums are highly concentrated products that offer targeted solutions in skin care. They can be used for many purposes such as moisturizing, anti-wrinkle care, spot lightening and skin tone equalization. Since serums contain small molecule formulas that can penetrate down to the lower layers of the skin, their effects are fast and deep. They are usually applied to cleansed skin, after toner but before moisturizer. For example, serums containing vitamin C give the skin a glow, while those containing hyaluronic acid provide intense moisture. Retinol-based serums are used to combat signs of aging and can reduce fine lines with regular use. However, it is recommended to start with a low concentration as retinol ingredients may initially cause irritation. When choosing a serum, skin type and needs should be taken into consideration. For daily use, it can be applied twice a day, morning and evening. Clean and toned skin is essential for serums to be effective.