Editorial for the special issue on: transitions in society, energy, ecology, materials and other areas

* e-mail: j 2020 was a very special year, indeed! The COVID-19 pandemic reminded us that viruses, including pathogenic ones, are part of the biodiversity of the ecosystems in which we are immerged and that a very strong interaction can take place, at the scale of thePlague or the Influenzapandemics of the historical past. This caused time to hiccup and to slow down its pace formonths.The scientific life towhichwewere used suddenly froze. Thus, the 14 Society and Materials Conference, SAM-14, planned for 11-12 May, 2020 in Bordeauxat theuniversityandENSAM,had tobecancelled. Everything was ready to go when that decision was made. A program had been arranged from the answers to the Call for Papers received in January. Keynotes speakers had accepted to come to Bordeaux to share their worldviews. The Jean-Sébastien Thomas Award had been attributed to a “best paper” among a set of candidates. The decision was then made to organize a new event in May 2021, which would be virtual and was to be called SAM-15. Papers selected for SAM-14 would be automatically accepted for SAM-15, if authors were willing to present an updated version in 2021. However, some authors had already sent written contributions to the conference organizing committee and it was decided to collect and present them in a special issue of Matériaux et Techniques, if they willing to go along with this format and passed a further peer-reviewing test. The present special issue is the result of this exercise, where 9 peer-reviewed papers based on contributions to SAM-14 are brought together, out of 38 presentations and keynotes, and 16 posters. The issue is organized around the theme of transitions, a lively, contemporary concept at the