How can we support pupils' engagement in argumentation? Should argumentation be explicitly taught or rather embedded in the learning tasks? Which design principles are related to the goal of promoting argumentation in the science classroom? Are they the same as design principles for constructivist learning environments? How can research explore these features of learning environments supporting argumentation?The above excerpt comes from a 4th-grade classroom (9-10-year-olds), during the process of jointly planning a field trip by teacher and pupils, including decisions about topics to be studied and methods to study them. The teacher uses an analogy between ecology and classroom studies that is the reverse of another analogy found in educational papers (see for instance Doyle, 1977) that propose viewing the classroom as a complex system of relationships and interactions similar to the relationships in ecosystems. Here the presence of the researcher, Ramón López, in the classroom is used to exemplify both the need for an approach to the pond as a whole and of doing it in the field. Implicit in the teacher analogy between the classroom and the pond is the goal of promoting pupils' reflection about their own learning processes and about the ways of constructing knowledge concerning the pond.The use of this analogy can be seen as connected to the third, fourth and fifth questions formulated in the first paragraph, the last concerning research about argumentation learning environments, a research tightly interwoven with the design principles aimed at promoting argumentation, the subject of the third and fourth questions. These design principles intend, among other goals, that pupils reflect about their own learning. The relationships among designing environments to promote argumentation and investigating them can be connected to the impact on some science educators, like myself, initiating S. Erduran and M. P. Jiménez-Aleixandre (eds.), Argumentation in Science Education.91