Microscopic chaos is the dynamical randomness in the collisional motion of atoms and molecules in fluids. This chaos animates different mesoscopic stochastic phenomena and, in particular, the reaction-diffusion processes. For different chemical reactions, we show how the reaction rate can be related to the characteristic quantities of chaos like the Lyapunov exponents and the Kolmogorov-Sinai entropy which are associated with a fractal repeller. In spatially extended deterministic chaotic systems, chemio-hydrodynamic modes with exponential decay are shown to exist as Schwartz-type distributions associated with Pollicott-Ruelle resonances. The problem of entropy production is also discussed.
