In this chapter, the groundbreaking concept of organ-on-a-chip technology was introduced and its importance in biomedical research was examined. The use of organ-on-a-chip platforms offered a unique opportunity to mimic complex organ microenvironments and study organ function in a controlled laboratory environment. The fabrication techniques and materials used in organ-on-chip systems were discussed, highlighting the advantages of this technology, including its potential for high-throughput screening, reduced animal testing, and the ability to replicate disease conditions. However, the challenges and limitations associated with organ-on-a-chip models were also acknowledged. The design concepts of specific organs on chips, such as the heart, lung, brain, kidney, liver, intestine, vasculature, and skin, were briefly discussed, explaining their unique functions and contributions to disease modeling and drug development. Additionally, the application of organ-on-a-chip technology in cancer research was examined, with a focus on tumor-on-a-chip models and their materials. Finally, the emerging human-on-a-chip concept, which integrated multiple organ systems into a single device and enabled more comprehensive studies, was presented.