A glycan is a type of carbohydrate made up of sugar molecules linked together in various ways. These structures can be simple, like disaccharides, or complex, like polysaccharides. Glycans play essential roles in biological processes, including cell recognition, signaling, and immune responses. Glycans are often found attached to proteins and lipids, forming structures known as glycoproteins and glycolipids. These modifications can influence how cells interact with each other and their environment. Understanding glycans is crucial in fields like biochemistry and medicine, as they are involved in many diseases and are potential targets for therapies.