Scientist Wambugu works with farmers in Kenya, a country in East Africa.She helps them grow bigger and better crops.She is especially interested in finding simple ways to produce more food.In the past ten years, she has spent much of her time studying sweet potatoes.They are an important food in her part of Kenya.A virus kept attacking the plants.It stopped the sweet potatoes from growing properly.Some farmers, says Wambugu, lost three quarters of their crops because of the virus.Even expensive chemicals and complicated machines could not eliminate the virus.Wambugu went to war against the virus.She searched for a weapon that could save the sweet potatoes.This led to a laboratory established in St.Louis, Missouri.The lab works on genes.Genes exist in the cells of living things and could tell a plant to produce pink flowers or an animal to grow black hair.Now scientists have found ways to move genes from one living thing to another.This process is called genetic engineering.By making use of it, Wambugu created a sweet potato plant that could fight against the virus.She tested her research in Kenya, and her plants produced magnificent sweet potatoes.That’s just the beginning, the scientist believes.Genetically modified foods, she argues, could help farmers in poor countries grow crops desperately needed.“What farmers need”, Wambugu says, “is technology that is packaged in the seed.” No expensive chemicals, no complicated machines—just create strong plants that farmers can grow simply, and fewer people will go hungry.Nevertheless, critics warn that it is dangerous to put genes into species where they do not belong.Because genes tell the cells in plants or animals how to grow, it is not known for sure how the mixing of genes will affect plants or animals in the long term.With that in mind, many people worry about the safety of genetically modified foods.