Richard Feynman, Nobel Laureate in Physics who developed quantum electrodynamics once wrote “What I can not create, I do not understand”. This basic principle has become a sort of a mantra for engineering, and also guides research in my laboratory. We aim to decipher how the brain develops because we think that this will help us to understand how it works. We are particularly interested in the development of the cerebral cortex: the nerve tissue that covers most of our brain and that is visible from the outside. The cerebral cortex enables us to perceive the world around us, to think and make decisions. This amazing structure consists of several billion neurons, and it is folded into many gyri and sulci to fit inside our skull. Our laboratory aims to understand the general principles governing the formation of the cerebral cortex, which consists of hierarchical networks of excitatory and inhibitory neurons with complementary functions. In the next years, we will focus on the molecular mechanisms controlling the precise development of different classes of inhibitory neurons. In particular, we would like to understand how much of the information needed for their development is genetically encoded, and what is the influence of the environment in the formation of this complex brain structure. We also aim to shed light into the genesis of important human disorders that are caused by disturbances of the normal development of the cerebral cortex, such as epilepsy, autism or schizophrenia.