Animal testing has long been necessary for a drug to gain approval by the US Food and Drug Administration—but it may be on its way out.But as we get into some of these more difficult diseases, especially neurological diseases, the animal models just aren't serving us as well,” says Paul Locke, a scientist and lawyer at Johns Hopkins University who studies alternatives to animal testing.“We need new ways to really unlock the molecular mechanisms that are causing these diseases, and the alternatives I think hold great promise.”Locke and other advocates point to studies that have shown animal testing to be an unreliable predictor of toxicity in humans.Researchers at the Wyss Institute and elsewhere have gone on to create chips that simulate the liver, stomach and intestine, brain, skin, and more, using them to test the effects of drugs and environmental toxins.Though no bigger than a pea, these models have some of the characteristics of full-size hearts and brains, and because they’re grown in a lab dish, they provide scientists with a detailed window into how organs form and develop."