Soy milk or soymilk is a plant-based drink produced by soaking and grinding soybeans, boiling the mixture, and filtering out remaining particulates. It is a stable emulsion of oil, water, and protein. Its original form is a natural by-product of the manufacture of tofu, but was long unpopular because its oligosaccharides caused flatulence and discomfort in lactose-intolerant adults. It became a staple of East Asian cuisine over the last few centuries, after it was discovered that prolonged heating eliminated this effect. It has become more popular in Europe and North America over the last few decades, as production techniques were developed to give it a taste and consistency more closely resembling dairy milk. Along with similar vegetable-based "milks" like almond and rice milk, soy milk is now often used as a substitute for dairy milk by individuals who are vegan or lactose intolerant.