Emulsifiers are used in creams and lotions to mix water with oils. Since water and oil do not mix but stay separated, an additional agent (emulsifier) is necessary to form a homogenous mixture keeping water and oil together. There are 2 types of emulsifiers. Oil-in-water (o/w) emulsifiers keep oil drops packed in water, while water-in-oil (w/o) emulsifiers keep water drops packed in oil. W/O emulsifiers are used for a fatty feel (e.g night & sun protection creams). O/W emulsifiers are used more in moisturizing products (e.g. body lotions, day creams). O/W is the most common type of emulsions.