The book you hold in your hands is the work of compiling both historical and current information about many aspects of the relationship between lipids and cell function. In it, the researchers led by Professor Dr. RuiCuri discourse on a subject that to a greater or lesser extent is part of their investigative interest. Therefore, part of the findings presented here are from experiments conducted by the authors themselves. The book consists of six chapters arranged in a sequence that begins with a brief history of the identification of the essential properties of fatty acids, followed by a synthetic overview on structural and biochemical aspects of fat. In the following three chapters the reader will dive deeper into the knowledge of one of the classes of lipids- the Fatty Acids. In these chapters are developed extremely current and interesting subjects such as- modulation of intracellular signaling by fatty acids, lipotoxicity and therapeutic applications. In the last chapter we present the main techniques used to determine the lipid content of tissues and cells. We believe that this material maybe useful both for that reader who wishes to begin his study of fatty acids and need a starting point, as to one who already being familiar with this topic wants better understand and apply a technical protocol. Finally, we hope that your journey through the world of lipids be useful and enjoyable for your purposes. Enjoy your reading!