Aperol introduced the revolutionary idea of an aperitif with an alcohol content of only 11%, yet only took off in Italy after World War II. Today, it is produced by Gruppo Campari and enjoyed by over 3.4 million Italians. Like Campari, Aperol's recipe has remained unchanged since its inception, and the exact ingredients are held a tight secret. It certainly contains bitter orange, gentian, rhubarb, and cinchona, lending the drink its unique color and flavor. In Italy, Aperol is also available as a pre-bottled cocktail, Aperol Soda. In bars it is often served with vodka, fruit juice or on the rocks. Aperol Spritz, the most famous Aperol-based cocktail, combines Aperol and Prosecco, and unsurprisingly is most popular in the Veneto.