Obtaining a map of brain connectivity at the single-neuron level is an ongoing goal in neuroscience; however, current axonal tracing methods are limited by the time required to manually reconstruct projections from stacks of microscopy images. Winnubst et al. have now boosted the efficiency of this process through the development of a semi-automated pipeline for brain-wide two-photon imaging and neuronal reconstruction. Using this approach in mice, they have created an online database of over 1,000 reconstructed neurons, identified projection cell types and provided insight into the principles of brain connectivity.