Consumers around the country will soon know just by looking at the packaging of popular brands such as Cocoa Puffs cereal or Yoplait yogurt whether or not they contain genetically modified ingredients. Their maker, General Mills, plans to make that information visible on its products nationwide. Other major food companies have since followed, including Kellogg, ConAgra and candy maker Mars. Campbell Soup publicized the same decision in January. The companies are all responding to a Vermont law requiring the labelling of genetically modified foods starting in July, and to pressure from consumers and advocacy groups to reveal more information about controversial ingredients. Between 70% and 80% of packaged food in the US contains ingredients from genetically modified organisms. A genetically modified organism is created in a laboratory by taking genes from one species and inserting these genes into another to breed certain characteristics. Big food companies have historically fought mandatory labelling. They worry that genetic manipulation creates an impression that the food is unnatural or unhealthy. Meanwhile, anti-GMO advocacy groups, such as Center For Food Safety, and food makers who say they don't use GMOs, including Plum Organics and Nature's Path, also cast the fight as an issue of transparency, and accuse food makers of hiding important information from the public.