From neuronal action potentials to cell signaling during embryogenesis, the communication between healthy cells is fascinating. And when it goes awry, very bad things happen (e.g. cytokine storms).
Outside the biomedical context, the subject matter of the details of cell-cell communication is of considerable interest. The NYT covers this wonderful article in SCIENCE today here. This is why places like the Marine Biological Laboratory in Woods Hole are so special–by studying non-model organisms (i.e. other than mouse, fruit fly or zebra fish) we gain insights from evolution on how these capabilities of cells came to be.