The patterns of gene expression that define differentiated cells are controlled by complex regulatory networks of transcription factors and microRNAs. Johnston and Hobert now identify a new component of the network that controls left/right asymmetry in the gustatory neurons of Caenorhabditis elegans - the zinc finger transcription factor lsy-2 (see p. 5451). The nematode's gustatory neurons ASE left (ASEL) and ASE right(ASER) are morphological mirror images but have left/right asymmetric functions. The researchers show that, although lsy-2 is expressed in both ASEL and ASER, it is a permissive factor for the expression of the microRNA lsy-6 in ASEL - lsy-6 is a component of the regulatory network that controls ASEL fate. By identifying a factor that is involved in the spatial expression of a microRNA gene, the researchers provide an important new insight into how terminal cell fates are specified.