During the late 1990s to early 2000s, pharmacogenomics matured from a conceptual framework into a concrete research program linking genetic variation to drug response. The dominant pattern involved dissecting pharmacokinetic pathways, particularly cytochrome P450 metabolism and conjugation processes, and exploring how regulatory mechanisms modulate enzyme expression. The era saw emphasis on mechanistic insights, the development of early pharmacogenetic testing concepts, and integration of these ideas into clinical translation through knowledge resources and decision-support considerations.