Cellular Automata

In the 1940s, John Von Neumann and Stanislaw Ulam wanted to design a computer able to self-repair. In the real world an object can be produced only from a more complex object. Consider replicating a piece of paper. To create one, we need to have a more complex object, a printer, the printer is a much more complex system than paper, and to create a printer, we need a lot of smaller components which are themselves complex and so on.