This book highlights the application of microfluidics in cell biology research, chemical biology, and drug discovery. It covers the recent breakthroughs and prospects of organ-on-a-chip, human-on-a-chip, multi-organ-on-a-chip for personalized medicine. The book presents the preclinical studies of organs-on-a-chip, concepts of multiple vascularized organ-on-chips, application of organ-on-a-chip in blood-brain barrier model, culture and co-culture of cells on multi-organ-on-chip and parameter measurements in microfluidic devices. It underscores the advantage of microfluidic devices for developing efficient drug carrier particles, cell-free protein synthesis systems, and rapid techniques for direct drug screening. Further, it entails human-on-a-chip for measuring the systemic response as well as immediate effects of an organ reaction on other organs. In summary, this book reviews the development of a microfluidic-based organ-on-a-chip device for the preclinical evaluation, ADME studies of drugs, chemicals, and medical devices. This book is a valuable source for pharma companies, product developers, students, researchers, academicians, and practitioners.