In vitro models of bioavailability and metabolism are laboratory-based systems designed to simulate key physiological processes involved in the digestion, absorption, and biotransformation of nutrients and bioactive compounds. These models provide controlled, reproducible environments that enable us to investigate mechanisms of intestinal transport, enzymatic metabolism, and cellular responses without the complexity and cost of human or animal studies (We collaborate with others when working with animals or humans). We often perform in vitro digestions coupled with the Caco2 cell model to understand the absorption of iron and carotenoids. These models serve as important screening tools that help prioritize compounds, refine hypotheses, and inform the design of subsequent in vivo and clinical investigations.