For complex systems have a more popular definition: by a large number of interacting components, there is no central control, through the simple operation rules produce complex collective behavior and complex information processing, and through the adaptive learning and evolution. Including the brain, immune system, cell, insect society, global economy, biological evolution, world wide web and so on.
We can also understand complex systems simply as systems between order and chaos. It’s not like an orderly system like an alarm clock or an integrated circuit board, and it’s far from the unpredictable chaotic systems of hurricanes and turbulence. Imagine you are playing a game of control balls with your mobile phone. The ball is driven by random forces and will roll on the seesaw. You need to tilt your phone to avoid falling balls. If the ball is about to move to the left, tilt your phone to the right and keep it in the middle of the seesaw. This is not completely fixed in a certain position, but there is no persistent disequilibrium of the seesaw, which is where the complex system is located. This place — often called the edge of chaos — is that the various elements of the system are not at rest in a certain state, but there is no turbulence to the place where it dissolves; It is that life has enough stability to support its existence, and enough creativity to make itself truly the place of life.
Because complex systems don’t have central controllers, we make it self-organizing, because simple rules produce complex behavior in unpredictable ways, sometimes called emergent.
We can also see a complex system involving many research fields, including: system theory, nonlinear dynamics, game theory, collective behavior, complex network pattern formation, evolution and adaptability, and so on.