Sialic acid is a natural sugar building block found on the surfaces of our cells. It acts as a protective and recognition molecule and plays a central role in the development of the nervous system. Following the modular principle, individual components can be swapped for new building blocks, thereby altering the properties of the sugar. Researchers at Hannover Medical School (MHH) have investigated how these building blocks reach their target. These fundamental findings are also significant because certain influenza and coronavirus strains specifically use modified sialic acids as receptors to enter host cells.