Once the forgotten sidemen of the bar world, bitters – herbal tinctures that add big flavor to mixed drinks – are everywhere now, available in a variety and quality not seen in the past 100 years. (You've seen them behind bars in those dark, squat little bottles.) Not bad for a product that started off in the 1700s as snake oil – that is, herbal tonics marketed as medicine, made by infusing high-proof alcohol with plant parts from rose petals to citron peel and wormwood. The result may not have been strictly medicinal, but it was packed with intense bitter flavors – which, 19th-century bartenders discovered, could transform a cocktail from so-so to sublime in just a few drops, balancing booze with woody, fruity, herbaceous, spicy, or floral notes. By the turn of the 20th century, bitters were an essential part of the bartender's arsenal. But Prohibition wiped out most of the country's bitters biz, and for decades after, the word bitters was synonymous with one product: Angostura, in the brown bottle with the yellow cap and oversize label. Though still the industry standard, Angostura has a lot of company these days from producers all over the country, in flavors ranging from celery to Jamaican jerk. Don't let the options overwhelm you – the best can add surprising complexity to drinks you make at home. Remember that bitters are the salt and pepper of the cocktail world, supporting players designed to accentuate and amplify a cocktail's inherent flavors, not steal the show. Feel free to experiment: Floral or citrus bitters complement the vegetal flavor of gin; chocolate bitters enhance the dark, mellow notes in aged spirits like rum or scotch; peach bitters play perfectly off the ripe fruit of bourbon. Add these flavor bombs by the dash or drop, and stop when your drink tastes delicious.