Odors play a key role in the personal care industry. They are the raison d' etre of the multi-billion dollar fragrance industry. Cosmetic products have base odors to be fragranced, or at least masked. The major marketing difference between shampoos and bath products is usually fragrance. Fragrance is typically the most expensive ingredient in a cosmetic formula. Yet despite the unquestioned importance of fragrance, our knowledge of the sense of smell is often surprisingly sketchy.