Sugar structures are ubiquitous in the human body. They surround the cells like a scaffold to protect them on the one hand and to enable interactions with other compartments on the other hand. The so-called glycans occur as glycolipids, proteoglycans or glycoproteins. Glycosylation is a complex posttranslational modification involving many different enzymes. The structural complexity of oligosaccharides allows them to function as information carriers. Many proteins have specific sugar structures that contribute decisively to the function of the protein.