The brain is the most complex organ in humans. Its primary units, the neurons, communicate with each other and are organized in networks. Characterizing these neuronal circuits is of great interest to science, and the ability to modulate circuit nodes and control neuronal functions using optogenetic tools has revolutionized research. In the research group of Prof. Kristina Herfert, various stimulation techniques are used to investigate their effects on the functional, metabolic, and molecular connectivity of the brain in both healthy and pathological conditions