In physics, photon bunching refers to the statistical tendency for photons to distribute themselves in bunches (super-Poissonian statistics) rather that at random (Poissonian)[1]. Thermal fields are examples of photon bunching. Their statistic can be observed as photons that arrive more simultaneously (positive correlation) at detectors. This can disturb our understanding of classical particles, which tells us that non-interacting particles should know nothing about each other, and so should arrive independently of one another. This apparent contradiction is explained by recognizing this not as a particle effect, but rather as a wave effect. Photon bunching is predicted by quantum mechanics, and manifests experimentally in the Hanbury-Brown and Twiss effect, which itself can be understood classically as a pure wave effect.