Most potential new drugs fail when they're tested in people. These failures are not only a major disappointment – they sharply drive up the cost of developing new drugs. A major reason for these failures is that most new drugs are first tested out in mice, rats or other animals. Often those animal studies show great promise. But mice aren't simply furry little people, so these studies often lead science astray. Some scientists are now rethinking animal studies to make them more effective for human health.