Flax is a multi-purpose crop with emerging markets for its industrial, food and feed uses. Linseed oil extracted from seeds is used for environment friendly industrial applications such as linoleum flooring, manufacturing of paints, stains and varnishes. Flax EFAs are important players in many metabolic processes in cell biology not only as cell membrane structural components but also as storage lipids. The free FAs are involved in several metabolic pathways such as storage lipid synthesis in developing seeds, cutin and suberin production, and cuticular wax layer synthesis in different tissue types and developmental stages. This book summarises current knowledge of different lipid classes found in flax, their localisation and genetic control, and the regulation of flax seed lipid biosynthesis.