Nitro cold brew is one of coffee’s strongest ties to beer. It’s the thing we grasp for when trying to make coffee relatable and relevant to those outside the industry. If you walk into any café and ask a barista what nitro cold brew is, inevitably they’ll make a Guinness or Stout comparison. And even though we’re still justifying its existence, nitro cold brew is everywhere.

In 2016, Starbucks announced that it would be adding nitro lines to 2,500 of its 8,500 U.S. stores; by the end of this year, they’ll be installed in every single U.S. location. The trend has become so popular that even Dunkin’, the ubiquitous East Coast coffee chain known for serving coffees “light and sweet,” has added nitro lines to select stores, and you can find whole sections of grocery or big-box stores dedicated to RTD nitro drinks.

Although nitro now feels ubiquitous in the coffee and beer worlds, it’s a relatively new innovation in both industries. As Evan Rail detailed in a different GBH article, nitro was a happy accident first developed by Michael Ash in the 1950s while he was working on improving Guinness’ shelf life. Adding nitro to coffee also began as a fringe idea about seven years ago. Following many unexpected twists and turns, it has since grown into a phenomenon—albeit a controversial one.