Physarum polycephalum, a single-cell organism known as slime mold, builds complex web-like filamentary networks in search of food, always finding near-optimal pathways to connect different locations. In shaping the Universe, gravity builds a vast cobweb-like structure of filaments tying galaxies and clusters of galaxies together along invisible bridges of gas and dark matter hundreds of millions of light-years long. There is an uncanny resemblance...