 If a system such as a plant, a building, or a car shows organization, we tend to assume that someone or something must have designed it in that particular order. Self-organization is the idea that this type of global coordination can instead be the product of local interactions. The theory of self-organization has grown out of many different areas from computer science to ecology and economics. Out of these areas have emerged a core set of concepts that are designed to be applicable to all self-organizing systems from galaxies to living cells. But let's start by talking a bit about organization itself. Organization is a highly abstract concept, but we can lose the equated to the idea of order, with its opposite being what is called entropy or disorder. Order and entropy are typically measured by scientists in terms of information. That is, the more information it takes to describe something, the more disorder the system is said to be. An example of this might be a piece of metallic substance consisting of tiny magnets called spins. Each spin has a particular magnetic orientation, and in general they are randomly directed and thus cancel each other out. This disorganized configuration is due to its heat energy causing the random movement of molecules within the material. When we cool the material down, the spins will spontaneously sideline themselves so that they all point in the same direction. To describe the state of the spins in this ordered system would involve far less information relative to its original state that required a unique value for each randomly directed spin. This process of magnetization is often cited as an example of self-organization, that is the spontaneous appearance of order or global coordination out of local level interactions. But let's take a closer look at how this happens. As we cooled the material down there was some area that had by chance some spins pointing in the same direction. Their alignment generated an increased magnetic force that was exerted upon its neighbors, creating what is called an attractor state, attracting other spins to this particular configuration. Each time another spin aligned itself with this particular attractor state it augmented the force that exerted upon other spins through what is called a positive feedback loop that would cascade through the system until all elements were aligned within this new regime. Another example of self-organization through positive feedback is what is called the network effect. When the more people that use a product or service the greater its value becomes. The telephone and facebook are such examples becoming more useful as more users join. In this way local connections between individuals can rapidly form into global patterns. The network effect illustrates the positive relations or synergies between elements that can be created when they coordinate. It is due to the presence of these synergistic relations that the system as an entirety can be said to be more than the sum of its parts through a process that is called emergence. And colonies are classical examples given of emergence, and governed by very simple rules and only local interactions can through their combined activities generate colonies that exhibit complex structures and behavior that far exceed the intelligence or capability of any individual ant and thus it is said to have emergent properties. Ant colonies also illustrate the decentralized structure to self-organizing systems. The queen does not tell the other ants what to do instead each ant reacts to stimuli in the form of chemical scent exchanged with other ants. In this way organization is distributed over the whole system all parts contribute evenly to the resulting arrangement. As opposed to centralized structures such as most social organizations that are often dependent upon a single coordinator this decentralized structure that is inherent to self-organizing systems often gives them a resilience and robustness. Any element that is damaged can be simply replaced by any other. Whether this self-organizing system is a social institution, a technology or ecosystem for it to sustain itself over time it must be able to withstand change and intervention from its environment requiring the system to be both robust to perturbations and capable of adapting to change. The generation of noise and variation within the system is a classical mechanism for achieving this. Without diversity a system can become rigid and develop into what is called a critical state. An example of self-organized criticality could be an economy whose many industries have developed a dependency upon petrochemical fuels. This lack of diversity in energy sources means a small disruption in the supply chain of petroleum from the system's environment could have large global consequences. Conversely systems with a high degree of diversity between elements are often more robust as the variety between elements makes them more effective at absorbing change. Ecosystems are classical examples of this generating a large variety of species that make it capable of surviving significant changes within its environment. Thus we can see how evolution is a core concept in understanding the dynamics of self-organizing systems whereby attractor states and feedback loops generate the system and periodic perturbations from its environment work to select the most adapted or fittest elements. As information technology is enabling new forms of organization people within many domains are faced with the practical challenges of how to design and manage self-organizing systems such as computer networks and new forms of social collaboration all of which are making self-organization theory particularly relevant to the challenges we face in the 21st century.