Experiments are essential for both doing science and learning science. The aim of the German youth science fair, "Jugend forscht," is to encourage scientific thinking and inquiry methods such as experimentation. Based on 57 interviews with participants of the competition, this study summarises students' conceptions and steps of learning about experimentation, taking into account age disparities. Five distinct subdomains of learning were identified in which learning processes may occur. These subdomains are procedure, purpose, material, control, and time. The three separate age groups used slightly different concepts but all the participants took the same or very similar steps of learning independent of their age. Two main reasons for conceptual developments could be detected: Firstly, the participating students had the opportunity to work using methodology similar to the commonly accepted scientific path of knowledge. Secondly, due to communication processes during the competition, a purposive reflection of their own project was promoted. With respect to different educational levels, experimentation proves to be a complex scientific framework that will be learnt step by step throughout students' education. We therefore argue for a stronger anchoring of research experiments embedded in open or authentic inquiry to be included in science lessons at school.