Lipids possess a wide range of biological activities in plants, animals and humans. They also serve as important components of our daily diet and provide both energy and essential fatty acids; they also act as carriers of fat-soluble vitamins and help in their absorption. Lipids are crucial as a heating medium for food processing and affect the texture, mouth feel and flavour of foods. Structured lipids (SL) are triacylglycerols (TAG) modified to alter the fatty acid composition and/or their location in the glycerol backbone via chemical or enzymatic means. SL may offer the most efficient means of delivering target fatty acids for nutritive or therapeutic purposes as well as to alleviate specific disease and metabolic conditions. This document discusses chemistry, composition, classification, function, occurrence in food and biological activities of lipids. It also sheds light on different aspects of structured lipids, including SL applications, synthesis (chemical vs. enzymatic), SL and aquaculture and future considerations for SL.