In humans and animals, fat cells produce and store fat in special organelles, which are specialized subunits within the cell, called lipid droplets. The lipid droplets make up the largest part of the volume of these fat cells, also known as adipocytes. Adipocytes fulfill vital tasks protecting our organs, as well as parts of the body that are sensitive to cold, and they serve as a source of reserve energy. But when we eat too much fat-rich food, the adipocytes and thus the fat deposits grow excessively, leading, in the worst-case scenario, to the development of pathologies such as obesity and obesity-related diseases. In contrast, certain individuals develop a disease because no lipid droplets are formed at all. The associated clinical picture is called lipodystrophy, in which the affected individuals are unable to store lipids and thus become seriously ill.