The document summarizes key developments in the structural characterization of G protein-coupled receptors (GPCRs), beginning with the 1975 structure of bacteriorhodopsin determined by Henderson and Unwin, showing its 7 transmembrane alpha helical structure. It then discusses important milestones such as the 1983 cloning of bovine rhodopsin, the first GPCR cDNA; the 1986 cloning of the beta-2 adrenergic receptor, the first non-sensory GPCR; the 1988 cloning of the 5-HT1A receptor, the first "orphan" GPCR to be deorphanized; and the 1991 crystal structure of rhodopsin, the first GPCR structure. The document concludes with the