RÜDIGER KLEIN and his research group are interested in the question of how newly born cells, so-called neurons, communicate with other cells during embryonic development and how this communication shapes the brain. During development, neurons explore their environment for the presence of chemical signals. One family of such chemical signals are called FLRTs. It is assumed that these FLRT proteins tell the neurons in which way to migrate from the inner to the outer layer of the cortex and, thereby, control cortex folding. As Rüdiger Klein explains in this video, the researchers manipulated genes of mice to find out how exactly this mechanism works. Their results suggest that there is an inverse correlation between the levels of FLRT and the degree of cortex folding: the less FLRT, the more folding we see. Their findings offer new insights into the mechanisms of the folding of the human brain.