In cellular automata, simple rules create elaborate structures. Now researchers can start with the structures and reverse-engineer the rules. Neural cellular automata self-assemble into whatever shape you desire. Michael Waraksa for Quanta Magazine Introduction Alexander Mordvintsev showed me two clumps of pixels on his screen. They pulsed, grew and blossomed into monarch butterflies. As the two butterflies grew, they smashed into each other, and one got the worst of it; its wing withered away. ...