We report an exploratory talk based, whole class plenary intervention, in relation to students' understanding of everyday measures and measurement, in a grade four classroom at a grade 4-6 school in Sweden. Extended, project related, teacher-researcher collaboration forms basis for such cultural historical activity theory or CHAT based efforts. As formative intervention, the conduct of the plenary is not pre-determined but embedded in ongoing curricular realities, with the agency of students and teacher promoted, pedagogical ideas reutilised and the role of researcher viewed as supporting design and growth of the intervention. Under Charlotta's guidance as teacher, the plenary is opportunity for her students to examine improbable scenarios such as, Can Eva and Anton measure the length of Sweden on foot, Can Lars and Iris measure their age in decimeters. A zone of proximal development is created, in which students make the transition from spontaneous to scientific concepts and learn how various units of measurement are objects-that-can-be-used-for-certain-purposes. With opportunity for critical and reflective inquiry, in a plenary designed to lead development, Charlotta's students look beyond the making of rote measurements and articulate a theory of measure in nascent terms. Such a landscape of teaching-learning is finally understood in terms of the nature of talk that was facilitated, the manner of pedagogy utilised, the style of teaching exercised and the kind of learning that was demanded of her students.