Lipids (fats and oils) are an extensive range of organic molecules that activate several functions in organisms. Lipids are essential components of our diet, focusing on their important contribution in energy, representing 9 kcal/g (or 37.7 kJ/g), and by some components relevant to the metabolism, such as essential fatty acids, fat soluble vitamins and sterols (cholesterol and phytosterols). Besides this, lipids have vital roles in human growth and development, along with promoting, preventing and/or participating in the pathogenesis or eventually in the treatment of various diseases. This book demonstrates a comprehensive analysis of the structure and metabolism of lipids.