In the literature, learners' cognitive development is mainly discussed with respect to changes in learners' content-dependent knowledge (conceptual change or growth). Additional dimensions of time and complexity may also be taken into account to describe cognitive processes in at least three dimensions. We discuss these three dimensions of content, complexity, and time theoretically and show empirically what results can be found with such a framework. The primary database consists of 27 students who worked in groups of three on physics tasks during three sessions in an experimental setting. All activities were videotaped and analyzed in great detail. Results indicate that students' meanings always refer to a narrow area of content, are developed bottom-up with respect to complexity, and show time-dependent dynamics in which maxima of 30 seconds and 5 minutes are important time scales. Comparison with outcomes of additional experimental settings on the same topic with more and less advanced students indicate the results to have a greater validity. (Contains 5 figures, 2 tables and 5 footnotes.)