A drop of dye added to a glass of water undergoes ordinary diffusion. However, when placed on the surface of a foam, the dye spreads differently—diffusion becomes anomalous. An example of this is the pattern on the froth of a cup of cappuccino.

Source: [Phys.org](https://phys.org/news/2026-06-diffusion-links-foam-physics-voting.html)

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