The article, "Rules for Biologically Inspired Adaptive Network Design" by Atsushi Tero and colleagues, demonstrates cellular intelligence. The slime mold Physarum polycephalum has a track record of being masters at solving puzzling mazes. Thus, an interesting experiment was conducted to test this ability.
The Physarum was put in a nutrient-like maze such that the food sources represented major cities in Japan. At first, the Physarum explored their surroundings randomly. Then it reorganized itself in an even more efficient way than Japan's current design! To abide by the Law of Conservation of Energy (law of thermodynamics), the shortest path to food wins.