This text is written particularly for those who, with some knowledge of chemistry or biochemistry, need to know more about the nature of lipids and of fatty acids. Much of the readership will be employed in the food industry since 80% of the world production of oils and fats is eaten by humans and another 6% goes into animal feed. They will need to understand the materials they handle; their origin, their chemical nature, the effects of processing, and their physical, chemical, biochemical, and nutritional properties. Another group of readers will be employed in the oleochemical industry, modifying the material produced by nature for the benefit of human kind. They will have to understand the constraints of production and of chemistry within which they work and to be aware of the present state of knowledge about these materials.