Gilles Debrun and Pauline de La Boulaye, curators of *Inventaires #3 Architectures Wallonie-Bruxelles*, highlight four projects from the 2016–2020 edition of the collection. In this book, due to be published this autumn, the reuse of materials is one of the main themes, and environmental criteria were a key factor in the selection of 45 exemplary buildings.

Antoine Lavoisier is the author of the famous maxim: ‘Nothing is lost, nothing is created, everything is transformed’, published in 1789 in his *Elementary Treatise on Chemistry*. This statement seems to apply almost perfectly to the currently fashionable concept of circularity.