In order for precision medicine to be successful, accurate characterization of the patient is necessary. A variety of biomarkers could provide the necessary data, collected through a variety of 'omics techniques. However, identifying and characterizing biomarkers that accurately reflect a physiological state (normal or diseased), or response to a particular drug or therapy, has turned out to be challenging. Add to this the complication that biomarkers may differ between population groups, or indeed between individuals, and that tracking these biomarkers as the patient’s status changes can be onerous, and the future of precision medicine could be described as bleak. Yet this pessimistic outlook has not stopped researchers from pushing forward in their search for accurate and robust biomarkers, which they hope will help to predict the risk of disease, ascertain the probability of positive clinical outcomes, and evaluate therapeutic efficacy. In this supplement to Science, these important topics are discussed, with a focus on advances in precision medicine research in China.