Anyone who gardens is keenly aware of the smell of soil. And while it doesn’t occur to most of us to eat dirt, the smell is compelling and can be profoundly nostalgic.

As Swedish scientists have discovered, this strange and pheromonic scent, geosmin, comes about because of the interrelation of an insect (springtails) and bacteria. Apparently, humans are more sensitive to the smell of geosmin than sharks are to the smell of blood. It is said that one drop is enough to scent an Olympic-size swimming pool. It also turns out that the stuff is used in perfumes, provided it is used in strengths of the magnitude of .001%. That means my one milliliter purchase of geosmin 100% will make a thousand liters of tincture. I keep mind stronger—about .01%--so it maintains its strength when diluted with other ingredients.

I like to pair geosmin with other compounds that evoke water, air, or ozone.