How do you know if the chemicals in the stuff you use and eat are safe? Only a small fraction of the thousands of chemicals in use today have been thoroughly tested for safety. Part of the problem is that how we test chemicals now is slow, expensive, and relies an awful lot on animal testing. However, a new approach is being developed by the US Environmental Protection Agency, the National Institutes of Health, and the Food and Drug Administration. It’s known as TOX21. Using innovative techniques such as high throughput screening and computational biology, TOX21 a first step toward revolutionizing how we ensure the safety of the substances we use.