Over the last two decades, the education system has witnessed a shift from summative, product-oriented assessment towards formative, process-oriented assessment. Among the different learning and assessment initiatives introduced in the slipstream of this paradigmatic turn, the portfolio seems to have become one of the most popular. By redescribing the portfolio from a systems theoretical point of view, this article discusses established expectations of the portfolio in relation to transparency in learning, reflexivity and self-assessment. It shows that the majority of the literature deals with "what" questions, and that the portfolio is expected to handle a number of challenges with regard to the documentation of learning processes and achievements as well as the conditioning of learning activities. Descriptions of "how" the portfolio works are sparse. Based on systems theory, the paper adopts a "how" perspective: How does the portfolio redescribe learning? How does it scaffold and organise communication? One conclusion is that systems theory allows us to redescribe the portfolio as a teaching technology, which, by scaffolding both reflection and reflexivity, produces particular conditions for the stimulation and observation of learning, thus increasing the complexity of observation of learning.