What’s perhaps most extraordinary is that scent lodges itself largely in the long-term memory system of the brain. And yet, we remain inept at mapping those links and associative chains when it comes to describing smells and their emotional echoes. To shed light on how perfumery plays into this paradox, Ackerman offers a taxonomy of the basic types of natural smells and how they became synthetically replicated, unleashing an intimate dance of art, science, and commerce:

All smells fall into a few basic categories, almost like primary colors: minty (peppermint), floral (roses), ethereal (pears), musky (musk), resinous (camphor), foul (rotten eggs), and acrid (vinegar). This is why perfume manufacturers have had such success in concocting floral bouquets or just the right threshold of muskiness or fruitiness. Natural substances are no longer required; perfumes can be made on the molecular level in laboratories. One of the first perfumes based on a completely synthetic smell (an aldehyde) was Chanel No. 5, which was created in 1922 and has remained a classic of sensual femininity. It has led to classic comments, too. When Marilyn Monroe was asked by a reporter what she wore to bed, she answered coyly, “Chanel No. 5.” Its top note — the one you smell first — is the aldehyde, then your nose detects the middle note of jasmine, rose, lily of the valley, orris, and ylang-ylang, and finally the base note, which carries the perfume and makes it linger: vetiver, sandalwood, cedar, vanilla, amber, civet, and musk. Base notes are almost always of animal origin, ancient emissaries of smell that transport us across woodlands and savannas.

Smells are direct links to parts of the brain. Like hyperlinks on the Web. Cool!