Tonic water is the latest ingredient to show up in trendy espresso drinks. Unexpected? Definitely. But after one taste, we swear you’ll be wondering: Where has this been all my life?

The truth is, espresso tonics—sometimes called Caffe tonics or black tonics—have been around for a while. They’re on menus in trendsetting cities like Tokyo, Toronto, Melbourne, Stockholm, Helsinki, and Berlin. And now they’ve touched down in San Francisco thanks to Kevin Bohlin, founder of 7-month-old Saint Frank Coffee shop, who discovered them through a Swedish micro-roaster at an international barista competition.

The concept is as simple as it sounds: A long shot of espresso is poured over a fizzy glass of artisanal tonic water on ice. But the result is surprisingly complex—a sweet and citrusy, creamy and effervescent, so-beautiful-you-can’t-help-but-Instagram-it concoction with a Guinness-style frothy head. It’s a cup of coffee and a palate cleanser all in one.