Perfumery
I know how to build a perfume from three ingredients: a top, a middle and a base. Top notes are things like citrus oils which evaporate quickly, within about 15 minutes from the skin; middle notes are floral or herbal, like jasmine or lavender which could last for an hour; and base notes are woody, like amber or vanilla which you can smell for hours after you first apply them. (Ruth Mastenbroek, perfumer)