Microfluidic technology provides opportunities to create in vitro models with physiological microenvironment for cell study.Introducing the identified key aspects,including tissue-tissue interfaces,spatiotemporal chemical gradients,and dynamic mechanical forces,of living organs into the microfluidic system,"organs-on-chips"display an unprecedented application potential in a lot of biological fields such as fundamental physiological and pathophysiological research,drug efficacy and toxicity testing,and clinical diagnosis.Here,we review the recent development of organs-on-chips and briefly discuss their future challenges.