At no other time in its history has humankind been as concerned about good health. Lifestyle habits are promoted as indispensable allies for the daily prevention against so-called metabolic diseases. Paradoxically, the world has never been so obese, while the beauty canons have never been so skinny! However, there is more to energy balance than alterations in body weight. In the 1990s, it was found that fatty acids not only function as fuel molecules only, but also serve as signaling molecules. They bind nuclear hormone receptors, the Peroxisome Proliferator-Activated Receptors, commonly referred to by the acronym PPARs. PPARs are transcription factors that directly control the expression of genes of metabolism, thereby impacting a multitude of pathways crucial for whole body physiology. PPARs are also activated by synthetic agonists, which are drugs used for lowering triglycerides and blood sugar. This book features articles that address tools for the identification of novel PPAR ligands, as well as the roles of the receptors in several organs, such as the brain, heart, liver, adipose tissue, gut, and muscle. As such, this book documents the multifaceted roles of these nuclear receptors that continue to attract significant attention, not least because of their still not fully realized potential to treat several health conditions.