This article, delivered as one of two keynote lectures at the International Standing Conference for the History of Education (ISCHE) in Milan in September 2022, offers an example of an autosociobiographical approach to the history of education, in which the life story of the author is entangled with the collective movement of a generation of pedagogues, to capture "the lived dimension of History", quoting the winner of the 2022 Nobel Prize in Literature, Annie Ernaux. It describes the journey of the "centres of interest", a pedagogical technology closely linked to the Belgian educational reformer and scientist Ovide Decroly, which evoked positive and negative emotions among the Spanish pedagogical explorers who visited Decroly Schools in the first decades of the twentieth century. This technology found its way into material school culture in Spain, grew into a veritable mania, but died an early death after the Spanish Civil War. It returned in a new guise, the "globalised didactic units", thanks to textbooks written by the first post-war generations of pedagogues, who rediscovered Decroly's ideas, and developed an emotional bond with these textbooks, and -- without knowing it -- also with their pre-war predecessors.