Most neuronal connections in the brain are organized into precise topographic maps for processing information efficiently. Despite the importance of maps for brain function, our understanding of topographic mapping has remained limited by our inability to observe maps forming and maturing directly in vivo. In their latest study titled "Live imaging of retinotectal mapping reveals topographic map dynamics and a novel role for Contactin-2 in map sharpening", Drs. Olivia Spead and Cory Weaver, Trevor Moreland and Dr. Fabienne Poulain generated a new transgenic zebrafish line to observe the visual topographic map forming and maturing in a living animal. They found that some visual connections are first broadly established but then refine as they mature, and that the adhesion molecule Contactin-2 is required for this refinement to occur. A great wrork!