The present paper presents a method for the observation of interactions in families with adolescent children, aimed at studying families' microtransitions. The data include six family interviews which were video-recorded in laboratory; each family had at least one adolescent child (aged 13 to 15). The interviews were conducted with the technique of circular interviews, which involved all members and is particularly important for a process analysis of microtransitions. The procedure for the analysis of interactions comprised two main categories: coordinations and oscillations; our intent is to operationalize these categories as privileged indicators of microtransitions. The data analysis allowed us to describe the forms taken by these categories during families' interactions and to reflect on their importance for a better understanding of developmental family processes.