Complex adaptive systems can do some amazing things. They heal when they are injured. They make decisions with incomplete information. They develop over time, but in a way that after the fact appears planned. The rules and structures that created them can be destroyed and replaced with new rules. They are ordered enough to have repeatable functions but not so ordered as to be inflexible. If the environment changes, the internal structures and flows will change too. Somehow complex adaptive systems can self-organize. This chapter presents several possible ways in which a system might reach a point of criticality, including self-controlling order parameters, the self-organization of internal rules or constraints, tuned chaos, and functional tensegrity. While not dismissing these as possibilities, the emphasis is placed on self-organized criticality. The sandpile model is introduced in several different variations along with the system concept of an avalanche. A focus is also placed on systems that tune to their environment, with Conway’s law, paradigm shifts, and tangled hierarchies serving as conceptual examples. Applications are given for several complex systems including evolution, technology, healing and the human body, and the economy. More provocative topics are how self-organized criticality and other complex systems topics may be applied to understand creativity, morals, consciousness, free will, and what it means to be human. The chapter concludes with questions for either reflection or group discussion as well as resources for further exploration.