For centuries, many cultures have used scents and odors for a variety of purposes. From the earliest civilizitions, humans have created and used scents to mask unpleasant odors and to enhance other, more appealing ones. To find out what makes humans so responsive to natural and synthesized fragrances, series host and naturalist Diane Ackerman investigates the role of incense in Oman, visits a perfume factory in New Jersey, traces a smell from outside the body to the part of the brain that stores memories and emotions, and examines how different animals use their sense of smell.