A slime mold is not one thing but many: a single giant cell containing millions of nuclei, spreading across a forest floor as a living yellow web. It has no brain, no neurons, nothing that deserves the name of a nervous system. Yet placed in a maze with food at two ends, it will, over hours, retract from dead-end corridors and thicken the single tube that traces the shortest path between the two meals. Researchers who scattered oat flakes in the pattern of a nation's cities found the mold linking them with a network strikingly similar to the rail lines engineers had designed. It is tempting to call this intelligence, but the scientists are careful. The mold does not plan; it has no representation of the maze inside it. What it has is a body that flows toward food and away from light, thickening where nutrients reinforce a flow and thinning where they do not. Behavior that looks like foresight emerges from simple local rules applied everywhere at once. The lesson, the researchers argue, is not that the mold is secretly clever, but that problem-solving we assume requires a mind can sometimes fall out of physics and chemistry alone.