Franck Polleux is a Professor at The Scripps Research Institute in La Jolla, California. He was an Associate Professor at University of North Carolina – Chapel Hill. Dr Polleux was trained at INSERM U371 in Bron, France and then in the Department of Neuroscience at Johns Hopkins University in Baltimore. Introduction The human brain is composed of billions of neurons each connected through thousands of synapses. Some of the most challenging questions in neurobiology are: first, how is this incredibly complex connectivity emerging with high fidelity during development? and second, what are the cellular and molecular mechanisms underlying specific neurodevelopmental disorders such as autism? This issue of Current Opinion in Neurobiology contains 23 articles from some of the leading scientists in the field, who review exciting progress in our understanding of normal and pathological mechanisms of brain development.