CMOS imagers have enabled the development of integrated, miniature, low-cost, digital and smart imaging systems. The course provides an overview of the fundamentals of CMOS imager design and operation. It summarizes the sensor architecture and pixel approaches, and reviews the state-of-the-art imagers. It analyzes imaging performance CMOS imagers, and discusses relative merits of different implementation approaches. By presenting examples of on-focal-plane processing circuits, including analog-to-digital converters, the course discusses design considerations involved in digital imager integration and synthesis. The course concludes by outlining the main hurdles that the CMOS imaging technology needs to overcome, and approaches for doing so.