KNOWLEDGE of the nature of the heterocysts of blue-green algae has been limited by the lack of suitable techniques for investigation of the physiology and biochemistry of these puzzling structures.

Filamentous cyanobacteria respond to combined‐nitrogen scarcity by converting selected vegetative cells into heterocysts, specialised microoxic factories for atmospheric nitrogen fixation.

Multicellular cyanobacteria do something strikingly sophisticated with their DNA, toggling key genes on and off as day turns to night so different cells can specialize without starving the colony of ...