A thin slice of wood under a special microscope bursts into bright colors. This isn't paint; it's light passing differently through cellulose fibers, the thin ropes that build cell walls. The colors reveal how these fibers are arranged.
It turns out that in different cells, the fibers are arranged differently. In strong fibers, they twist like a screw; in water-conducting vessels, they form swirls around openings; and in ray cells, they weave together like a basket. The same patterns occur in liquid crystals, substances that flow but maintain order. When a liquid crystal solidifies, the pattern remains forever.
So, the cell wall of wood was once liquid. Cellulose fibers floated in it, arranged themselves into spirals and swirls, and then solidified. In this way, wood preserves a memory of how it grew.
The thickness of a fiber cell wall is about 4 μm, and the pitch of the cellulose spiral is approximately 16 μm, meaning the fibril makes only a quarter turn across the entire wall thickness.
In Greg Egan's novel 'Permutation City', the architecture of living buildings is based on self-assembly from biopolymers. The idea that wood is a frozen liquid crystal recalls such self-organizing structures.