Organ‐On‐a‐Chip (OOC) is a multichannel 3D‐microfluidic cell‐culture system incorporated in a chip that simulates the behavior of an organ. This technology relies on a multidisciplinary science that benefits from and contributes in the progress of many fields including microbiology, microfluidics, biomaterials, and bioengineering. This review article summarizes the progress and achievements of various organ‐on‐chip technologies. It highlights the significant advantages of this technology in terms of reducing animal testing and providing personalized medical responses. In addition, this paper demonstrates how OOC is becoming a promising and powerful tool in pharmaceutical research to combat diseases. It predicts not only the effects of drugs on the target organs but also, using body‐on‐a‐chip systems, it may provide insights into the side effects of the drug delivery on the other organs. Likewise, the models used for the construction of various organ‐on‐a‐chip devices are investigated along with the design and materials of microfluidic devices. For each OOC, the integrated monitoring devices within the chips (e. g., sensors and biosensors) are discussed. We also discuss the evolution of FDA regulations and the potential in the near future for integrating OOCs into protocols that support and reduce the need for and the failure rates in preclinical and clinical studies.