If you scatter seeds haphazardly, the seedlings will tangle into chaos. But if you lay them out in neat rows, the field will grow in an orderly fashion. A similar principle works with bacteria. Colonies of elongated cells usually churn with disordered flows, but scientists have found a way to impose order from the very start.

Spores of the bacterium Bacillus subtilis were laid out on a surface using capillary assembly — a method that places each spore at a precise spot with a precise orientation. When the spores germinated and grew into chains of cells, it turned out that if the initial orientations were parallel, the film was ordered over millimeters. If the spores were randomly oriented, chaos ensued.

Then it gets more interesting. The ordered film, as it continued to grow, bent synchronously, like a single sheet. The scientists described this behavior with a model based on the mechanical properties of individual filaments. They then used the order to create films with local optical anisotropy: that is, regions that refract light differently. Such materials could be useful for living displays or sensors.

So the initial conditions, how the spores are laid out, determine the fate of the entire colony. This is not just a new tool for biologists, but a step toward programmable living materials.