A cilium is not a cilium is not a cilium: signaling contributes to ciliary morphological diversity.

Mukhopadhyay and colleagues reveal in this issue of Developmental Cell that signaling mediated by a specialized neuronal cilium in C. elegans affects its structure. The finding that this cilium is modified in response to the cues it transduces suggests that cilia may not be static antennae, but organelles whose functions are shaped by their signaling activities.