The organs-on-a-chip platforms seek to recapitulate human organ functions at microscale by integrating microfluidic networks with three-dimensional tissue models, which are anticipated to provide robust and accurate predictions of drug/toxin effects in the human body. We are developing the state-of-art organ-on-a-chip platforms with integrated bioreactors and microfluidic modules. The efforts represent a critical step towards animal-free toxicology tests to eventually achieve personalized precision medicine.