La version française suit la version anglaiseOn May 18, 2021, the United Nations General Assembly declared 2022 the International Year of Glass, highlighting the role of glass in scientific, economic, artistic and cultural fields. Glass is essential to many vital technologies, facilitates the transition to a more sustainable world and beautifies our lives. Everyone is familiar with the everyday life glass that has accompanied mankind for over 10,000 years, such as the first cut obsidian, or more recently, the first Roman glass blown over 2000 years ago. For the man on the street, glass is present in tableware, bottles for perfumery, cosmetics and pharmaceuticals, cookware, food packaging, flat glass for windows, mirrors and solar panels, as well as glass wool, fiberglass, glass for optics and photonics, and others special glass. Glass can be recycled ad infinitum, and there is ample evidence that it was recycled as far back as Roman times. Tomorrow's glass will make it possible to rebuild the human body using bioglass [1], and to store energy in new batteries with almost infinite capacities [2].In a recent issue of CR Géosciences, a series of articles showed that it is possible to obtain a glass with all types of atoms and chemical bonds [3]. But the question remains, "What is glass?".As early as the 1920s, some physicists proposed that glass could be the fourth state of matter [4]. Glass would be neither liquid nor solid, but would share certain properties of both, in a fixed disorder that could be relaxed. In the 50s and 60s, numerous theories emerged, ranging