Page 438: The Notion of Reversibility
Reversible cellular automata starting from random and simple initial conditions
Reversible cellular automata starting from random and simple initial conditions 2
Examples of reversible cellular automata starting from random and from simple initial conditions. In the upper block of pictures, every cell is chosen to be black or white with equal probability on the two successive first steps. In the lower block of pictures, only the center cell is taken to be black on these steps.

From Stephen Wolfram: A New Kind of Science [citation]