The complex functions of the cerebral cortex rely on neuronal networks of highly interconnected excitatory glutamatergic neurons and inhibitory GABAergic interneurons. Although comprising only a minority of all cortical neurons, GABAergic interneurons are crucially important for normal cortical functions. Deficits in GABAergic signaling are strongly implicated in a number of brain disorders including epilepsy, schizophrenia and autism spectrum disorders. GABAergic interneurons are highly diverse in their morphological and physiological properties, determining the specific roles of different GABAergic interneuron subtypes is therefore a fundamental yet challenging task in modern Neuroscience. Our research goal is to understand how GABAergic interneurons are organized to shape cortical network activity and plasticity, and how GABAergic circuits are engaged in neuropsychiatric disorders.