Few advances in neuroscience could have as much impact as a precise global description of human brain connectivity and its variability. Understanding this ‘connectome’ in detail will provide insights into fundamental neural processes and intractable neuropsychiatric diseases.The connectome can be studied at millimetre scale in humans by neuroimaging, particularly diffusion and functional connectivity Magnetic Resonance Imaging. By linking imaging data to genetic, cognitive and environmental information it will be possible to answer previously unsolvable questions concerning normal mental functioning and intractable neuropsychiatric diseases.Current human connectome research relates almost exclusively to the mature brain. However mental capacity and neurodevelopmental diseases are created during early development. Advances in fetal and neonatal Magnetic Resonance Imaging now allow us to undertake The Developing Human Connectome Project (dHCP) which will make major scientific progress by: creating the first 4-dimensional connectome of early life; and undertake pioneer studies into normal and abnormal development.The dHCP will deliver:• the first dynamic map of human brain connectivity from 20 to 44 weeks post-conceptional age, linked to imaging, clinical, behavioural and genetic information;• comparative maps of the cerebral connectivity associated with neurodevelopmental abnormality, studying well-characterized patients with either the adverse environmental influence of preterm delivery or genetically-characterised Autistic Spectrum Disorder; and• novel imaging and analysis methods in an open-source, outward-facing expandable informatics environment that will provide a scalable resource for the research community and advances in clinical medicine.