(Seeberger 2015-2017) The term "complex carbohydrates" refers to the multitude of sugar types (monosaccharides) in a carbohydrate. Whereas starch is a simpler carbohydrate built only from glucose, human milk oligosaccharides are constructed from three to five monosaccharide building blocks and therefore described as "complex carbohydrates". The term "complex carbohydrates" encompasses glycans which are mono-and oligosaccharides linked to lipids and protein. In contrast, the term "carbohydrates" describes molecules from monosaccharides alone. Of note, even "simple carbohydrates" can have a very complex structure because of the glycosidic bonds (connections between the building blocks) forming linear and branched 3D structures with isomeric variation.