systems differently. Systems have a history: The future behavior of a system depends on its initial starting point and subsequent history. Non-linearity: React disproportionately to environmental perturbations. Outcomes differ from those of simple systems. Emergence: Each system's internal dynamics affect its ability to change in a manner that might be quite different from other systems. Irreducible: Irreversible process transformations cannot be reduced back to its original state. Adaptive/Adaptability: Systems that are simultaneously ordered and disordered are more adaptable and resilient. Operates between order and chaos: Adaptive tension emerges from the energy differential between the system and its environment. Self-organizing: Systems are composed of interdependency, interactions of its parts, and diversity in the system. Modeling and simulation CAS are occasionally modeled by means of agent-based models and complex network-based models. Agent-based models are developed by means of various methods and tools primarily by means of first identifying the different agents inside the model. Another method of developing models for CAS involves developing complex network models by means of using interaction data of various CAS components. In 2013 SpringerOpen/BioMed Central launched an online open-access journal on the topic of complex adaptive systems modeling (CASM). Publication of the journal ceased in 2020. Evolution of complexity Living organisms are complex adaptive systems. Although complexity is hard to quantify in biology, evolution has produced some remarkably complex organisms. This observation has led to the common misconception of evolution being progressive and leading towards what are viewed as "higher organisms". If this were generally true, evolution would possess an active trend towards complexity. As shown below, in this type of process the value of the most common amount of complexity would increase over time. Indeed, some artificial life simulations have suggested that the generation of CAS is an inescapable feature of evolution. However, the idea of a general trend towards complexity in evolution can also be explained through a passive process. This involves an increase in variance but the most common value, the mode, does not change. Thus, the maximum level of complexity increases over time, but only as an indirect product of there being more organisms in total. This type of random process is also called a bounded random walk. In this hypothesis, the apparent trend towards more complex organisms is an illusion resulting from concentrating on the small number of large, very complex organisms that inhabit the right-hand tail of the complexity distribution and