You know that so-distinctive smell when rain falls onto earth…? We’ve been known to stand there, sniffing, for the sheer pleasure of it. Of course there’s no way to capture that smell naturally, so perfumers turn to chemistry to recreate that evocative scent. It can actually be created in nature through the activity of a bacteria called Streptomyces, along with a special enzyme. But mostly, when encountered in fragrance, it’s a synthetic.