Hydrosols are the co-product of essential oils in the steam distillation process. When a botanical, such as lavender, is steam distilled to produce essential oil, it also produces a water called "Hydrosol." Hydrosols posess the same therapeutic properties as it's counter part, essential oils, but are more gentle and less volitile than their co-product essential oil. You do not need to dilute hydrosol for topical application the same way you would with essential oils. They are also known as "floral waters" or "hydrolats."