Neuroscientists have revealed the precise connections between sensory neurons inside the retina and the superior colliculus, a structure in the midbrain. Neuropixels probes are a relatively recent development, representing the next generation of electrodes. Densely packed with recording points, Neuropixels probes are used to record the activity of nerve cells, and have facilitated these recent insights into neuronal circuits. The researchers describe a fundamental principle which is common to the visual systems of mammals and birds.