The Theory of the Five Elements is the idea that everything is connected to each other. It is formed around the five elements: wood, fire, water, metal, and earth. All substances on Earth are made of these elements.
Many philosophers, scientists, doctors, and researchers have linked the Theory of the Five Elements to other systems. In fact, Traditional Chinese Medicine has used the Theory of the Five Elements to the organs of the Human Body since as early as 770 BCE. 
Additionally, Chung, et al extended the application of this theory to cells in the human body. They correlate cells (as the smallest organism in the human body) to little organs and then apply the Theory of the Five Elements as follows:
● Endoplasmic reticulum (ER) corresponds to wood;
● Golgi apparatus corresponds to fire;
● Lysosome (including vacuoles) corresponds to earth;
● Mitochondria corresponds to metal;
● Plasma membrane (which envelopes the cell) corresponds to water. 
Wood: The Grounding Element
Wood is not simply representative of actual wood, but also represents the force of the element which is impulse, expansion, and development. Within the Theory of the Five Elements each element interacts with each other in different ways. These are referred to as cycles.
These cycles can be applied within nature, to relationships, or even to the human body. Depending on the cycle, different elements work with or against each other.
For wood, in the generating or supporting cycle, Fire unlocks Wood’s power; Wood unlocks Water’s power. The controlling and weakening cycles work to balance each other. Wood can break the Earth, but the Earth can bury Wood.
Within the human body, Wood represents unconscious and independent systems including
The liver and the gallbladder are associated with Wood due to their function of converting food to fuel in the body. 
At the cellular level, “The ER can be structurally and functionally divided into the rough ER and smooth ER. The rough ER is involved in the synthesis of protein due to the many ribosomes lining its inside, while the smooth ER is involved in lipid, glycogen, and steroid synthesis. Thus, the main function of the ER is synthesis.” 
 Chung, S. Et al. The Five Elements of the Cell. Integrative Medicine Research. 2017 Dec; 6(4): 452–456. doi: 10.1016/j.imr.2017.10.002 Times cited=6 Journal Impact Factor=2.368