Lipids, or fats, are used in living things in a wide variety of different ways, including energy storage and insulation. There are other beneficial properties that lipids can be used for, however, such as digestion and helping provide structure for certain parts of the structure of an organism's cells. In some living things, lipids are even part of the process by which hormones are formed in the body.
Lipids are a class of organic compounds that are greasy, insoluble in water and make up most of the different types of fats that exist in living things. Along with proteins and carbohydrates, lipids are an important structure in the formation and construction of cells.
Lipids are often known for their capabilities as a vehicle for energy storage. Lipids are energy dense, so they can store excess energy that has been consumed but not moved by an organism. According to Healthy Eating, approximately one-half of the energy used by an average human during a day comes from lipids. Lipids are also used for insulation purposes in a variety of animals. They form a layer that helps to protect the organisms from excessive temperatures. Some organs have layers of fat around them, composed of lipids, to keep them safe.