Understanding nanoscience and how nanotechnology works has proven challenging for high school students, especially if it is not one of the core concepts specified in the national science curriculum. Out-of-school activities can be adopted as a method for teaching the fundamentals of nanotechnology. This paper presents two cases: one from Germany and one from Turkey, where high school students attended one-day out-of school activities on understanding the working principles of Atomic Force Microscopy (AFM), including the related concepts of size and scale, and intermolecular interactions. In the German case, a teaching experiment group work activity included an educational AFM and introduced the students to this technique by using different kinds of media such as teaching models. The out-of-school activity in Turkey was designed to include guided-inquiry activities where students were asked to predict individually, work in groups, conclude individually, and discuss and conclude in groups. The results of the analysis showed that students easily understood the working principle of AFM, gained a deeper understanding of the concepts of size and scale, but also had difficulties in matching the right scale dimensions of objects, especially on the sub-micro level.