Technology is a compulsory subject at Swedish elementary schools and, according to the syllabus, helps students develop their ability to examine different technological solutions and reason how these solutions affect society, environment, and humans. An important challenge for educational research is to analyse and understand the consequences and impacts of technologies on students' learning, well-being, and participation in society. It is important to understand how technological systems work in order to orient oneself in modern society and to make well-informed decisions about what is good or bad use of technology. The purpose of this study is to further explore students' understanding of technological systems and their features through investigating the students' reasoning and collaboration in small-group interactions. We found a relatively large number of situations where students clearly demonstrate that they understand technological systems and the components and relationships among them. On the other hand, some situations indicate that students have difficulty explaining and understanding or realising concepts, theories, and relationships regarding technological systems. The findings need to be examined critically, although the students in this study were not used to this way of working with concepts or using images in their presentations. The study was conducted in the spring of 2016 at a compulsory school in the south of Sweden.