In the beginning, we started off with a very simple view of components and what they do. As we learned more about React and did cooler and more involved things, it turns out our components aren't all that simple. They help deal with properties, state, events, and often are responsible for the well-being of other components as well. Keeping track of everything components do sometimes can be tough.
This is a companion discussion topic for the original entry at http://www.kirupa.com/react/component_lifecycle.htm