How does a living thing fold itself into complex shapes without a brain, nerves, or muscles?
A new study of one of Earth’s simplest animals suggests the answer lies in a surprisingly elegant mechanism—more like origami than engineering.
Scientists at Stanford University have uncovered a previously unknown way that tissues can fold, by studying placozoa, tiny flat animals found in warm seas such as the Red Sea.
Placozoa are among the simplest animals known. They are little more than a thin sheet of cells, yet they can fold, crease, and unfold themselves into intricate shapes with remarkable precision.
The research, led by bioengineer Manu Prakash and graduate student Charlotte Brannon, was published in Proceedings of the National Academy of Sciences.
It reveals a new role for cilia—microscopic, hair-like structures that cover the surface of many cells and are usually known for moving fluids, such as clearing mucus from human airways.
In placozoa, cilia do something very different. Instead of just beating back and forth, the researchers discovered that these tiny structures actively “walk” along surfaces. As they do, they pull and guide the sheet of cells, shaping the animal’s body and causing it to fold in precise, repeatable ways.
What makes this finding so striking is that placozoa have no brain or nervous system to coordinate these movements.
The instructions for folding appear to be built directly into the physical and mechanical properties of the tissue itself.
In other words, the shape changes are not controlled by decisions or signals, but by simple rules embedded in how the cells interact—much like the rules that govern how a flat sheet of paper can be folded into a crane or a flower.
To illustrate this idea, the research team even created a stop-motion animation using folded paper, echoing the animal’s movements and highlighting the parallels between origami and biological form.
The discovery has big implications. Tissue folding is a fundamental process in biology. It shapes developing embryos, forms organs, and creates the folds of the human brain.
Until now, most explanations for tissue folding relied on muscles, internal forces, or complex genetic control systems. This study shows that even extremely simple organisms can achieve sophisticated folding using basic physical principles.
The findings also offer clues about early animal evolution. Placozoa resemble some of the earliest animals on Earth, which appeared hundreds of millions of years ago. The newly discovered folding mechanism may reflect one of the earliest ways that living tissues learned to shape themselves—long before brains or nerves evolved.
By revealing how complexity can arise from simplicity, this work not only deepens our understanding of animal life, but also opens new ways of thinking about development, evolution, and even bio-inspired design.
Sometimes, nature’s most advanced tricks come from its simplest creatures.
Source: Stanford University.
