The organ-on-a-chip (OOAC) technology stands at the forefront of emergent technologies, representing a biomimetic configuration of functional organs on a microfluidic chip. This technology synergizes biomedical engineering, cell biology, and biomaterial technology to mimic the microenvironment of specific organs. It effectively replicates the biomechanical and biological soft tissue interfaces, enabling the simulation of organ functionality and responses to various stimuli, including drug reactions and environmental effects. OOAC has vast implications for precision medicine and biological defense strategies. In this chapter, the authors delve into the principles of OOAC, exploring its role in creating physiological models and discussing its advantages, current challenges, and prospects. This examination is significant as it highlights the transformative potential of OOAC technologies in the 21st century and contributes to a deeper understanding of OOAC's applications in advancing medical research.