Glycosaminoglycans are clinically used heterogeneous polysaccharides drugs derived from animal sources. Miller R. Group works on applying genetic engineering of the GAG biosynthetic pathway in cells to generate materials that can be used to systematically develop instrumentation, such as mass spectrometry and single-molecule methods. Characterisation of the glycosaminoglycan sulfation code with its function paves the way for the development of sustainable lab-derived homogenous glycosaminoglycan drugs.