In this model, translated from the Complexity Explorables model “Particularly Stuck” (Janina Schöneberger & Dirk Brockmann), particle-agents move noisily around in space, slowly spiraling toward the center. One particle is already stationary at the center, considered the ‘aggregation,’ and when other particles collide with it, they become part of a growing, emergent structure. Although the byproduct of random movement, the structure appears to have a fractal logic, branching outward like coral, neurons, or other natural objects.