The brain contains thousands of types of cells, but it is only in recent years that these have been brought into focus, thanks to new techniques that can distinguish them based on their functions, morphology, physiology and electrical properties. Such fine resolution is essential to understand the brain, argues Dr Renata Batista-Brito, from the Albert Einstein College of Medicine. Her most recent research has uncovered a previously unknown role for a rare type of inhibitory neuron in the cortex. In this interview, she discusses the journey to finding the function of these cells, the nature of sleep, and the importance of believing in yourself.