The Drosophila larval visual system: High-resolution analysis of a simple visual neuropil

► In this study we describe the organization of the larval optic neuropile. ► We complement confocal microscopy with serial EM reconstruction. ► We follow the LON and its neurons from early larval stages into the adult. ► We characterize sensory endings of PRs and the LON-innervating neurons. ► For the first time we conclusively show synapses from larval PRs to target neurons.