We focussed on understanding the moment in teaching sequences when teachers structure the knowledge developed during laboratory work. We named these moments debriefings. To study debriefing, our theoretical framework brought into plays altogether conversational analysis and knowledge analysis. Knowledge was revealed during class interactions and its analysis involved facets of knowledge. Three types of debriefing were observed. The first type took place as if the teacher would review all questions of the laboratory work and provide their answers during a class discussion. The class discussion could be viewed as a conversation based on ternary exchanges. The second kind of debriefing involved a document provided by the teacher. This document summarised knowledge, either linking several units of laboratory work or one unit with other phases of teaching. Last, the third kind of debriefing was based on a lecture that cannot be modelled as a ternary exchange. The structure of such a lecture could either follow the organisation of the laboratory work or not.