Physarum polycephalum

Physarum polycephalum has become famous for solving computational problems without a brain, neurons, or any central processing unit. This slime mold exists as a giant single cell—a plasmodium—with thousands of nuclei sharing one continuous cytoplasm. The plasmodium can grow meters across, flowing through environments as it searches for food. Yet this brainless blob can find shortest paths through mazes, recreate efficient highway networks, and balance nutritional intake with remarkable precision.

The plasmodium's problem-solving emerges from simple physical rules. Cytoplasmic streaming—rhythmic pulses of cellular fluid—carries nutrients through tubular networks. Tubes carrying more traffic strengthen; underused tubes weaken and disappear. This feedback between flow and structure creates self-optimizing networks. When researchers placed oat flakes (food) at positions matching major cities, Physarum grew networks resembling actual highway or rail systems. The slime mold's solution wasn't designed; it emerged from local optimization rules operating across the entire organism.

Physarum's distributed computation has inspired algorithms for network design and optimization. The slime mold approach works where centralized planning struggles: in dynamic environments with incomplete information, where solutions must adapt to changing conditions. Engineers have used Physarum-inspired algorithms to design supply networks, computer connections, and urban infrastructure. Understanding how a single cell achieves complex optimization informs both biology and engineering of distributed systems.