Ambergris is an animal by-product that's been used for centuries in, as flavoring for food, and as an aphrodisiac. It's one of the world's most expensive substances.
Pretty glamorous, especially when you consider that ambergris is: whale poop.
Christopher Kemp is a molecular biologist at Michigan State University. He's written a book about ambergris called Floating Gold: A Natural (& Unnatural) History of Ambergris.
Kemp says ambergris is used in perfumes because of its musky scent that can hold together the other lighter tones. Besides, its fatty, cholesterol-rich texture can stabilize the fragrance and make it last longer on the wearer's skin.