Oligosaccharides are defined as short polymers of monosaccharide residues linked by glycoside bonds having a degree of polymerisation (DP) between three and ten units (IUPAC definition). They may be linear or branched and normally contain hexoses or pentoses individually or in mixtures. Other monosaccharides may be present including uronic acids, sialic acids and anhydro sugars. Linkages found include 1,4, 1,3 and 1,2 both a and b and some oligosaccharides, particularly those of mammalian origin including blood groups, N-linked glycans and human milk oligosaccharides occur in nature but many others originate as hydrolysis products of polysaccharides. Apart from the highly significant natural properties of the mammalian oligosaccharides in what has been termed ‘the sugar code’ (defining blood groups etc), oligosaccharides from polysaccharides (and their synthetic derivatives) are of great value in the food and pharmaceutical industries for example as fermentation substrates, surfactants, probiotics, excipients, emulsifiers and acidulants.