Microfluidic devices allow for precise control of the cellular and noncellular microenvironment at physiologically relevant length- and time-scales. These devices have been shown to mimic the complex in vivo microenvironment better than conventional in vitroassays, and allow real-time monitoring of homotypic or heterotypic cellularinteractions.Microfluidic culture platforms enable new assay designs for culturing multiple different cell populations and/or tissue specimens under controlled user-defined conditions. Applications include fundamental studies of cell population behaviors, high-throughput drug screening, and tissue engineering. In this review, we summarize recent developments in this field along with studies of heterotypic cell-cell interactions and tissue specimen culture in microfluidic devices from our own laboratory.National Science Foundation (U.S.) (Grant EFRI-0735997)IR&D Project DL-H-550151Charles Stark Draper LaboratorySingapore-MIT Alliance for Research and TechnologyNational Institute for Biomedical Imaging and Bioengineering (U.S.) (Grant EB003805)