The microbiome plays a major role in the biotransformation of nutrients and xenobiotics in the body, which can alter the pharmacology and/or toxicology of these chemicals. A clear example of this is how intestinal microbiota transform bile acids, which act as modulators at bile acid receptors (FXR and TGR5) to affect signaling pathways related to bile acid synthesis and energy metabolism regulation. Cayman offers a wide range of primary and secondary bile acids as well as cell-based assays for easy assessment of potential modulators of FXR and TGR5.