Incense is aromatic biotic material which releases fragrant smoke when burned. The term refers to the material itself, rather than to the aroma that it produces. Incense is used for aesthetic reasons, and in therapy, meditation, and ceremony. It may also be used as a simple deodorant or insectifuge. Incense is composed of aromatic plant materials, often combined with essential oils. The forms taken by incense differ with the underlying culture, and have changed with advances in technology and increasing diversity in the reasons for burning it.