This image shows the cochlea of a mouse embryo lacking the transcription factor Neurod1 in the ear. There is strong efferent innervation (green). Scattered spiral ganglion neurons and afferent radial fibers (red) are present. Afferents and efferents are overlapping (yellow) but the intraganglionic efferent bundle formation is missing, Afferents and efferents overshoot organ of Corti at its base, whereas mostly afferents prematurely innervate the outer-hair-cell region of the apex. For more information, see the article by Macova et al. (pages 984–1004).