Musk.

Original musk came from the gland of the Himalayan musk deer — animalic, urinous, narcotic. The species is now protected, and modern perfumery has shifted entirely to synthetic musks: clean, soft, slightly powdery molecules that mimic the warmth of human skin.

There are nitro musks (vintage, slightly sweet), polycyclic musks (laundry-clean), and macrocyclic musks (the closest to the original animal). They are the base of nearly every modern perfume — the velvet on which the other notes are painted. Worn alone, musk reads as freshly-laundered, intimate, almost imperceptible.