Diffusion is the process by which molecules spread from areas of high concentration to areas of low concentration. This natural phenomenon occurs in gases, liquids, and solids, driven by the random motion of particles. For example, when a drop of ink is placed in water, it gradually disperses throughout the liquid until evenly distributed. In biological systems, diffusion is crucial for processes such as cellular respiration and nutrient absorption. Cells rely on diffusion to transport essential substances across their membranes, ensuring that they maintain proper function and homeostasis. Understanding diffusion helps explain various natural and industrial processes.