Digalactosyldiacylglycerol (DGDG) is a major non-phosphorous galactolipid found in the thylakoid membranes of plant chloroplasts and in certain bacteria. Its structure consists of a diglyceride backbone where the two hydroxyl groups are esterified with two galactose sugar residues via a glycosidic linkage. This amphiphilic molecule is characterized by its polar galactose head groups and non-polar fatty acid tails. DGDG plays a crucial structural role in the formation and stability of photosynthetic membranes. It is essential for the proper assembly and function of photosynthetic protein complexes, including photosystem I and II. Beyond its structural role, DGDG is involved in membrane dynamics and may participate in stress responses. In research, it serves as a key component in studies of membrane biophysics, lipid-protein interactions, and plant physiology. It is also used as a standard in lipidomics and analytical chemistry for the identification and quantification of galactolipids in biological samples.