Organs-on-chips are microfluidic devices for culturing living cells in continuously perfused, micrometer-sized chambers in order to model the physiological functions of human tissues and organs. This technology holds great promise to revolutionize pharmaceutical drug discovery and development. It will enable faster, cheaper, physiologically relevant and more reliable (standardized) assays for biomedical science and drug testing. In particular, it is anticipated that organ-on-a-chip technology can substantially replace animal drug testing with using the by far better models of true human cells. Moreover organ-on-a-chip technology will find its application in personalized therapy in the context of ‘precision medicine’.