Understanding how cells from different neuronal and glial lineages contribute to functional circuits has been complicated by the difficulty in tracking cells as they integrate into brain circuits. Sudarov et al. (J Neurosci 31(30):11055-11069, 2011) used a powerful genetics-based lineage marking approach to birth date ventricular zone-derived cells in the mouse cerebellum. The authors use their novel tools to elucidate the spatial and temporal dynamics of how distinct ventricular zone lineages are generated and assemble into the cerebellar microcircuitry. In this journal club, we discuss and evaluate the author's major findings.