The decoding of the human genome was supposed to have been the dawn of the age of personalized medicine. It turned out, though, that health is affected by a lot more than genes. As scientists were already aware, the environment and life experiences also have a huge impact on disease. Researchers, such as Jeremy K. Nicholson, have worked to make sense of such complex connections. Instead of looking at genes, Nicholson, a professor of biological chemistry at Imperial College London, checked out metabolites: the molecules that arise when the body processes materials such as food, drugs, or pollutants. Starting in the early 1980s, he and others showed that metabolites differ in predictable ways between people who are sick and those who are well. Today, Nicholson is a leader in a growing field called metabolomics. Its investigators have shown that metabolites can distinguish people who have cancer, diabetes, or other illnesses from those who do not. Metabolomics has caught the eye, and the pocketbook, of the pharmaceutical industry. The field may eventually help medicine to reach that elusive goal of personalized healthcare, predicting whether a healthy person will get sick and whether a drug will work for one person but not for another. Bringing a new field to life in academe is not easy. Metabolomics requires exquisitely sensitive instruments to detect minute quantities of chemicals in urine, blood, saliva, or other fluids. Many of the achievements of the field have been to develop technologies and figure out ways to show the difference between "a humongous amount of data in condition A versus a humongous amount of data in condition B," says Ian A. Blair, a professor of pharmacology and chemistry at the University of Pennsylvania. Researchers still disagree over which are the best techniques, and the field remains limited by high start-up costs because of the expense of the instruments. The complexity of the work can also slow it down: With hundreds or even thousands of compounds in each sample, researchers must devise ways to pull out the information on the important molecules. A group at the University of Alberta hoped to help that process when it announced last year the completion of the Human Metabolome Project, which listed 2,500 metabolites and the spectra that 400 of the molecules produce on various instruments.