Reversible mixing
A highly viscous fluid fills the void between two concentric cylinders and food coloring is injected at localized points throughout the mixture along the outer wall. As we slowly rotate the inner cylinder, the colors seem to mix as expected. However, when the inner cylinder is rotated in the opposite direction, the colors seem to un-mix, seemingly violating the laws of thermodynamics. The slow mixing creates laminar flow of the colors and removes turbulence.