One of the most spectacular characteristics of Cellular Automata is the emergence of complex structures, revealing their self-organizing capabilities. This kind of structure may emerge in a previously stationary domain against a range of different backgrounds. It can take many different forms. Some are stable; others decay immediately after they have come into being; others break down into substructures that reassemble after a certain lapse of time; others may generate new structures or absorb existing ones. When they collide, they may survive, they may be annihilated, or they may give rise to a cascade of new structures of increasing levels of complexity. The literature refers to some of these structures as “gliders”.