Base notes are the scents that form the foundation of a fragrance. They are typically rich and deep, providing lasting impressions that linger after the lighter top and middle notes have faded. Common base notes include vanilla, amber, and sandalwood, which contribute to the overall character of the perfume. These notes are essential for creating a well-rounded fragrance, as they help to anchor the lighter notes and add depth. Base notes usually become noticeable after the perfume has been on the skin for a while, often lasting for several hours or even days, depending on the formulation.