Pierre Sinaÿ's scientific work focuses on the chemistry of carbohydrates and the understanding of the role of oligosaccharides in the living world. In the mid-1970s, Pierre Sinaÿ discovered and developed an effective method for oligosaccharide synthesis known as imidate glycosylation. This, by now allowing access to increasingly complex carbohydrate structures, is not unrelated to the development of glycobiology, the aim of which is to decode the meaning of this third alphabet of saccharides, which is in addition to that of proteins and nucleic acids. He synthesized the antigenic determinants of substances in human blood groups and then synthesized a complexly structured pentasaccharide representing the active site of heparin responsible for its antithrombotic effect. This last achievement demonstrates for the first time, without any ambiguity, the molecular basis of such an activity, commonly used in hospital medicine. This breakthrough in glyco-chemistry has led to the concept of conformational flexibility, which is crucial in heparinology. First materialized by the use of nuclear magnetic resonance, this concept was studied in detail using the chemical synthesis of constrained sugars adopting unconventional conformations. Pierre Sinaÿ has also discovered and developed a whole series of conceptually new reactions. Selective examples include the synthesis of spiroorthoesters by using selenium chemistry, the development of organometallic chemistry of anomeric carbon, the pioneering synthesis of C-disaccharides, electrochemical glycosylation and, more recently, a novel functionalization of cyclodextrins through a kind of molecular microsurgery in which aluminium derivatives are said to be the scalpel. For the first time, the existence of the glycosyl cation, an intermediate conventionally postulated during glycosylation reactions, could be formally demonstrated through chemistry in a superacid environment. A 4-volume book covers many aspects of carbohydrate chemistry and biology.