In fancy coffee shops across the country, caffeine addicts are increasingly asking for a new side item to go with their fix: oat milk.The milk substitute has become so popular in places like Brooklyn that shortages have broken out, and a grey market for the most sought-after brand of the stuff — Oatly — has popped up online. Sometimes liters of Oatly can sell for as much as $18 each.Oat milk was created in Sweden for lactose-intolerant people about two decades ago, and it caught on.The beverage industry has taken notice. New brands of oat milk are set to flood the U.S. market this year. Oatly wants to stay on top. So they're opening two U.S. factories, one in New Jersey and one in Utah.The increased supply will help make sure there's plenty of Oatly for Brooklyn and Los Angeles. But Sweden-based Oatly has bigger plans for its product. They want everyone to drink it.VICE News traveled to Sweden and Millville, N.J. — with a stop at a couple Brooklyn coffee shops in between — to get the story on Oatly and its future.This segment originally aired March 22, 2019, on VICE News Tonight on HBO.