Perfumes are composed of three structural parts — the top, middle, and base notes — to provide the first impression, body, and lasting impression of the fragrance respectively after the application of a perfume.

The top note, or head note, provides the initial scent that forms the first impression of the perfume. It has the following features:
 It is comprised of small light molecules that have a strong fresh scent but evaporate quickly, usually 5–30 minutes after application.
 Common top notes include citrus (lemon, orange), light fruits (berries), and herbs (sage, lavender).
The middle note, or heart note, masks any unpleasant initial impression of the base note and provides the main body of the scent.
 It is comprised of more complex molecules than top notes and has a more mellow, rounded, and balancing scent.
 It first appears 20–60 minutes after application, and usually lasts 2–4 hours.
 Middle notes are made from more potent florals and spices. Common middle notes include lemongrass, rose, geranium, jasmine, nutmeg, lavender, cinnamon, coriander etc.
The base note adds to the middle note to boost and deepen the existing body of the scent and provide its lasting impression.
 It is comprised of large heavy molecules to provide a rich and smooth nature to the scent.
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 It is typically not perceived until 30 minutes after application or during the dry-down period. Some can last over 24 hours after application.
 Common base notes include cedarwood, sandalwood, vanilla, amber, patchouli, oakmoss, and musk.