This book offers a detailed exploration of G-protein-coupled receptors (GPCRs), key membrane proteins that mediate cellular responses to diverse signals. It covers GPCR activation, regulation, structural advances, technological innovations, and drug discovery, emphasizing their crucial roles in physiology and therapy. By integrating molecular insights with clinical applications, the book bridges basic science and translational research in GPCR biology. GPCRs function as vital cellular communication hubs by activating guanine nucleotide-binding proteins (G proteins) to transduce extracellular signals into intricate intracellular pathways. These signaling cascades regulate processes such as cell growth, gene expression, and intercellular communication, crucial for maintaining cellular homeostasis. Disruptions in GPCR signaling are linked to diverse pathologies, making them prime targets for therapeutic intervention. The book begins with GPCR structure and activation mechanisms, followed by signaling networks and receptor regulation. It then covers breakthroughs in structural biology and cutting-edge research technologies. Drug discovery strategies, including allosterism and biased signaling, are explored next. Systems biology and molecular pathologies provide deeper insights into GPCR functions and diseases. The final chapters focus on cellular toxicity, preclinical to clinical drug development, and future research challenges. This resource is designed for researchers and scientists in molecular pharmacology, cell biology, and drug discovery, as well as graduate and postgraduate students. Pharmaceutical industry professionals, educators, trainees, and healthcare professionals engaged in GPCR-targeted therapies will also find this book an essential guide to the latest advances and clinical applications.