Photosynthetic bacteria helped shape Planet Earth. Among them are cyanobacteria that produced the oxygen in our atmosphere and made complex life possible, captivating scientists for decades. Now, researchers at the Institute of Science and Technology Austria (ISTA) report a surprising new discovery—a system thought to separate DNA has developed to sculpt the shape of the cell in cyanobacteria instead. The results, published in Science, shed light on how protein systems evolve and how multicellularity emerged in this type of ecologically essential bacteria.