Lipids are a heterogenous group of compounds widely distributed throughout the plant kingdom. In plants they occur in the seeds, nuts, and fruits; in animals they are stored in adipose tissues, bone marrows, and nervous tissues. They are found in all organisms as structural components of the cell membrane.

Based on the chemical composition, lipids may be classified into three subgroups. Simple lipids are those that upon hydrolysis yield an alcohol and one or more fatty acids. Oils, fats, and waxes are simple lipids. Compound lipids have elements such as Phosphorous, Sulphur, and Nitrogen in their composition. Derived lipids include hydrolytic products of lipids as well as other lipid-like compounds like sterols, carotenoids, essential oils, aldehydes, ketones, alcohols, hydrocarbons, etc.

Plants store excess energy as carbohydrates, which later are converted to energy-rich triglycerides. These are converted back to carbohydrates during germination. Triglycerides are found in seeds, which are the source of most vegetable oils. Plants contain storage lipids mainly in the seeds. Some plants store it in the pericarp (olive, palm, avocado) and rarely in tubers (tiger nut tubers—Cyperus esculentus). In seeds storage lipids may be accumulated in one or both of the main types of seed tissue, that is, embryo or endosperm. For example, in sunflower, linseed or rapeseed, lipids are stored in the cotyledons of the embryo and in castor bean, coriander, or carrot, the endosperm is the main site of lipid accumulation. Tobacco, however, stores lipids in both embryo and endosperm tissues.

Hydrocarbons and waxes are found on the cuticle of fruits and leaves and these serve as protective coatings and as aids of water retention. Carnauba wax, Japan wax, and Ouricury wax are some examples of plant waxes.

Lipids comprise 7% of the dry weight in leaves in higher plants and they are important as membrane constituents in the chloroplasts and mitochondria. The amount of lipids in plant parts vary from 0.1–70%.

Polar lipids— phospholipids and glycolipids are structural components of plant cell membranes. Galactolipid are unique plant lipids enriched in plant membranes, particularly chloroplasts. As plants have no mechanism for controlling their temperature, they must possess membrane lipids that remain mobile at relatively low temperatures.

In addition to serving the function of food or energy storage, fats and oils are important products pharmaceutically, industrially, and as food. They are of tremendous importance in nutrition as they rank the highest among food in calorific value. In addition, they find use for cooking, soap making, glycerol manufacture, and for medicinal purposes.