Perfumes are made up of three notes: The top notes scents that are perceived immediately, usually described as “fresh,” “assertive” or “sharp.” The compounds that contribute to top notes are strong in scent, very volatile, and evaporate quickly. The middle (or heart) notes compounds are usually more mellow and “rounded” emerging as the top notes dissipate. The heart notes form the main body of the perfume. Scents from this note appear anywhere from 2 minutes to 1 hour after the application of a perfume. The base note compounds are often the fixatives used to hold and boost the strength of the lighter top and heart notes. The compounds of this class of scents are typically rich and “deep” and are usually not perceived until 30 minutes after the application of the perfume or during the period of perfume dry-down.