gradient is a spontaneous mechanism of nature until reached at equilibrium, or maximal entropy of any system although the molecules would still move around with no net movement. Diffusion is a passive transport that does not need any input of energy and there are six main physical factors that affect the rate of diffusion: size of particle, diffusion distance, temperature, concentration difference, surface area, and permeability. The size of the particle is inversely proportional to the rate of diffusion as a smaller object can move faster at a given temperature. The rate of diffusion will decrease when the distance between two areas of different concentrations of particles is farther each other. The rate of diffusion increases while the temperature rises, giving more amount of energy available for more rapid, spontaneous movement of substances. The greater the concentration gradient between two areas of substances, the faster the diffusion will occur. When subjected to the perspectives of cells, it is important the cells export and import materials efficiently within the plasma membrane. Thus, the cells increase the surface-area-to volume ratio by regulating their sizes smaller to support their metabolic activity. The larger cells, such as nerve cells, use a tactic of being long and thin or forming many protrusions to interact with outer membranes. The semi-permeability of cell membranes protects the cell by controlling the movement of substances in and out of cells.[Figure 1] The basic fabric of the plasma membrane consisted of a glycerol molecule, two fattyacids, and a phosphate group modified by an alcohol forms a bilayer for cell membranes.