If you've been to Starbucks on a hot day in the last few years, you may have noticed a new pump in place. The keg to which this pump is connected appears to contain a stout rather than a refreshing light coffee, but it is actually the key to creating one of Starbucks' strangest menu items.

Starbucks' Nitro Cold Brew injects nitrogen into the brand's classic cold brew coffee, providing a velvety texture along with plenty of foam. While nitrogen taps won't soon be installed in the best coffee makers, they are certainly gaining steam in coffee shops around the world. But how does it work, and why did Starbucks publish a science book?

Starbucks' Nitro Cold Brew is the same unsweetened black cold brew that Starbucks has offered for years, brewed slowly over 20 hours and as uplifting as ever. However, the addition of nitrogen during the pouring process creates microscopic bubbles that give the coffee a creamier, lighter, fluffier texture.

Starbucks' Nitro Cold Brew doesn't even contain ice. This is because even tap water is cold enough, but adding frozen water would negatively affect the taste. However, a variety of flavors are available for in-store and to-go items.

Beginning in 2020, Starbucks also offers beverages in cans. Priced from $3.49 to $3.99, these cans will be available at Walmart, Target, Amazon, and other grocery stores nationwide. If you want to get really technical, there is also a home keg kit available for $149.95.

The question on the lips of many coffee lovers is certainly "why? While there have been many scientific innovations in the world of wacky coffee extraction techniques over the past few years, perhaps the most hipster is the addition of nitrogen to cold brew coffee. But when you dig into the science, it's easy to see what this gas can do for your morning energy boost.

Nitrogen is an inert gas, meaning it does not react with anything around it, but it also does not dissolve in water until it is pressurized. In other words, it does not change the taste (or harm the drinker) when added to a liquid beverage, but it forms small bubbles that provide a creamier mouthfeel.

Whether you're interested in trying Starbuck's Science Brew or want to keep coffee out of your chemistry kit, getting a cheap coffee maker for the kitchen will certainly cut down on the cash you spend at the cafe. We've rounded up the best espresso machines for those who still want the strength of a cold brew cup, or if you're looking for something more convenient, check out all the best Nespresso coffee makers.