Book excerpt: This book focusses on the latest results related to the field of bile acids as signaling molecules and describes how these receptors have become a major pharmacological target. It covers all major areas of research in this field, from genetics, chemistry, in silico modeling, molecular biology to clinical applications, offering a cross-country view of the functional role of bile acids as signaling molecules, virtually acting on all major areas of metabolism. While FXR and GPBAR1 are essential bile acid sensors that integrate the de novo bile acid synthesis with intestinal microbiota and liver metabolism, in a broader sense, BARs play a pathogenic role in the development of common human alignments including liver, intestinal and metabolic disorders, such as steatosis (NAFLD) and steato-hepatitis (NASH), diabetes, obesity and atherosclerosis.