The pyramid is not three layers — it is three evaporation rates

The “fragrance pyramid” is often taught as a simple design metaphor — three tiers, arranged for effect — but it describes something physically real: top, heart and base notes are named for how quickly their raw materials evaporate off skin, which is itself a direct function of molecular weight. Light citrus oils and aldehydes (top notes) have small, volatile molecules that evaporate within the first two hours for most wearers. Florals and spices (heart notes) sit in the middle. Woods, resins, musks and amber materials (base notes) have heavy, low-volatility molecules that can still be detectable a full day later.

A well-built formula doesn’t simply stack three unrelated accords — it accounts for the fact that the top notes will thin out and let the heart take over, and that the heart will in turn fade as the base, barely perceptible at first, becomes the dominant impression by evening. Get the balance wrong and a composition either has no “opening” worth remembering or collapses the moment the top notes clear.