Perfumery notes are separated into three classes: top/head notes, middle/heart notes, and base notes; which denote groups of scents which can be sensed with respect to the time after the application of a perfume. These notes are created carefully with knowledge of the evaporation process and intended use of the perfume.
Top or Head notes
The scents that are perceived immediately on application of a perfume. Top notes consist of small, light molecules that evaporate quickly. They form a person's initial impression of a perfume and thus are very important in the selling of a perfume. Lasts about 15 minutes after application (citrus, aromatics).
Middle or Heart notes
The scent of a perfume that emerges just prior to when the top note dissipates. The middle note compounds form the "heart" or main body of a perfume and act to mask the often unpleasant initial impression of base notes, which become more pleasant with time. This note is very often the selection criterion of a perfume. Lasts about 15-30 minutes (floral, green, fruity, spicy).
The scent of a perfume that apppears approximately 30 minutes after departure of the middle note. Base notes bring depth and solidity to a perfume.Lasts up to 24 hours (wood, balsamic).