Before there were molecular tools available to identify and study taste receptors, scientists predicted that there would be many taste receptors and they would respond to specific taste qualities. These predictions came as early as the 1930s, from the results of human psychophysical studies, which showed that some people were selectively unable to taste certain bitter compounds but had an otherwise ordinary sense of taste. These observations suggested that taste perception arose from several or many receptors, and that one receptor could be dysfunctional in some people, leading to a specific ageusia. Further insight came with the molecular discovery of the bitter and sweet/umami receptor families at the turn of the twenty-first century. The newly sequenced human genome allowed investigators to search for DNA motifs such as transmembrane domains, which were likely to be a feature of a taste receptor. Other molecular biology tools were also essential to these discoveries. Since then, scientists have made advances in understanding which taste receptors respond to particular ligands, and in understanding the regulation of taste receptor mRNA expression in taste and other cell types. Additional discoveries made in the last twenty years include the receptors for salty and sour taste and perhaps for the non-traditional tastes such as calcium and fatty acids. There have been a few surprises, including the pattern of taste receptor evolution. This pattern includes the expansion of the taste receptor families in some species and the loss of taste receptors in others, e.g., cats. One discovery that was not a surprise was the molecular basis for specific ageusias, which arise from segregating pseudogenes, receptors that are nonfunctional in some people but not others. The burgeoning availability of DNA sequences for many species and many people worldwide has opened the frontier to better understand the range of perceptual experience among all animals including humans.