Biological images can be cluttered to the point where near-neighbor algorithms are bound to fail. (a) Superposition of two successive frames in synthetic data mimicking particle transport via turbulent fluid flow. Particles in the first and second frame represented as light-colored spheres and dark-colored diamonds, respectively. (b) Trajectory track segments derived for particles in these two frames via the “passing messages between frames” method.291 It is obvious that nearest-neighbor algorithms would not work well for this data. Reproduced with permission from Michael Chertkov, Lukas Kroc, F. Krzakala, M. Vergassola, and L. Zdeborová. “Inference in particle tracking experiments by passing messages between images.” Proceedings of the National Academy of Sciences 107, no. 17 (Apr 27, 2010): 7663−7668.