How does the activity in the brain, generated spontaneously in the nervous system or triggered by external stimuli, control the organization of an entire neuronal network in the first weeks shortly after birth? This is one of the central questions of Julijana Gjorgjieva. Basically, it is about understanding on a theoretical level how mammalian neural circuits self-organize. But it is also about the connection between visual stimulus changes, for example during day and night, and neuronal network activity. For these and other diverse questions, Gjorgjieva uses computational and mathematical approaches and combines calculations on individual neurons with those of an entire neuronal network in modeling – and does so very effectively, also in collaborative work with experimentally oriented research groups.