This book introduces readers to the latest advances in G protein-coupled receptor (GPCR) biology. It reviews our current understanding of the structural basis of ligand binding and allosteric mechanisms, following a decade of technological breakthroughs. Several examples of structure-based drug discovery are presented, together with the future challenges involved in designing better drugs that target GPCRs. In turn, the book illustrates the important concept of GPCR biased signaling in physiological contexts, and presents fluorescent- and light-based methodologies frequently used to measure GPCR signaling or to trace their dynamics in cells upon ligand activation.  Taken together, the chapters provide an essential overview and toolkit for new scientific investigators who plan to develop GPCR projects. All chapters were written by experts in their respective fields, and share valuable insights and powerful methodologies for the GPCR field.