Top notes refer to the scent of a perfume that you sense from the moment you put it on until about an hour later. Perfume smells when its aromatic components are heated by heat and evaporate into the air. Top notes are made up of aromatic components that are easily volatile, such as citrus types that have a citrus scent and green types that have a fresh plant scent. The reason why citrus and green scents don't last as long as woody or oriental scents is because of their high volatility. When choosing a perfume in a store, we tend to focus on the top notes when we first put it on, but we recommend letting it sit for a while and then judging whether you like the scent as a whole, including the middle and base notes.