This book comprehensively and systematically introduces the latest research progress, challenges, and future directions of various healthcare information systems. Starting from the formation, development, and typical research achievements of medical informatics, the book provides a detailed overview of the more mature healthcare information systems, including electronic medical record systems, laboratory information systems, picture archiving and communication systems, clinical decision support systems, Internet of medical things systems, telemedicine systems and mobile health systems, etc. Additionally, it delves into the rapid evolution of the Internet hospital, proactive health systems, and intelligent systems for medical and elderly-care combination in the era of big data, focusing on the fundamentals of big data technology and the transformation of medical informatization. This book can serve as a reference for researchers or engineers with a certain professional background engaged in cutting-edge research related to medical and health information systems, as well as a teaching reference for graduate or undergraduate students in related fields.