Systems simultaneously have the characteristics of form and function. Form is what the system is. Function is what the system does. To aid in developing an understanding of form and function in systems and system thinking, we will use four running examples: an amplifier, a design team, the circulatory system, and the solar system. Figures 2.4 through 2.7 show simple illustrations or schematics of these four systems. Note that the examples are chosen to include built and evolved systems, as well as informational, organizational, mechanical, and natural systems.