Perfumes typically have three "notes" or layers of scent that are released over time. The top notes are the initial scents that are detected upon application, which may be light and refreshing, such as citrus or herbal scents. The middle notes, also known as the heart notes, emerge after the top notes evaporate and may be floral, fruity, or spicy. Finally, the base notes are the lingering scents that remain after the perfume has dried down, which may be earthy, musky, or woody.