Bitter, dark IPAs, or India Pale Ales, are one of the fastest-growing beers in America in terms of popularity. Many IPA lovers even don’t know why they enjoy the "bitter, floral, earthy, citrusy, piney, fruity, and, yes once more, bitter flavor notes," as described by VinePair, but this is why IPAs are so bitter in the first place.

Hops, the flower of a plant called Humulus lupulus, are one of the most important ingredients in beer, and adding more hops is what makes an IPA bitter. Other ingredients can add bitterness, such as fruits, herbs, and vegetables, but hops do most of the work, and adding hops earlier in the brewing process creates a more bitter beer.

The International Bitterness Units (IBU) measurement scale usually rates the bitterness of beers from one to 100 units, but some beers can contain up to 1,000 IBUs, and any brew over 45 IBUs is considered to be on the bitter end. IPA lovers obviously enjoy high-IBU beers and their almost aggressive flavors.