Calmodulin interactions with Ca2+ channels unify two vital but diverse functions: Ca2+ regulation of channels themselves and local Ca2+ triggering of nuclear transcription factors. Crucial to these functions are the number of calmodulins regulating each channel, and the number of calmodulins privy to the local Ca2+ signal of each channel. Mori et al. (see the Perspective by Levitan) fused calmodulin to the cytoplasmic tail of the channel protein. A single calmodulin could reproduce the Ca2+-dependent inactivation characteristic of the native channel. The local concentration of calmodulin at the mouth of the channel was estimated to be several orders of magnitude greater than that in the cytoplasm. This value corresponds to a swarm of about 25 calmodulins poised at the channel mouth, presumably ready to carry Ca2+ signals to various targets such as nuclear transcription factors.