To fully understand the disease processes and syndromes you may encounter in the field, it is important to have a working knowledge of cellular processes, i.e., what is happening at the cellular level to cause disease, organ failure, and eventually organism death. However, before any meaningful discussion on that level can happen, understanding what comprises normal is paramount. Disease processes and syndromes can then be looked at as a collection of deviations from normal, rather than as discrete and separate from each other. This chapter will cover normal cellular function, including cellular chemistry and metabolism, life cycles, and homeostasis, or how a cell maintains its steady internal equilibrium with its harsh surroundings. From there, the chapter will discuss what a disruption of these processes can do to the cell and, by extension, to the whole body in the general term known as shock.