Diffusion processes refer to the movement of particles from an area of higher concentration to an area of lower concentration. This natural phenomenon occurs in gases, liquids, and solids, driven by the random motion of molecules. An everyday example is the way a drop of food coloring spreads in water, illustrating how substances mix over time. In biological systems, diffusion is crucial for processes like cell respiration and nutrient absorption. Cells rely on diffusion to take in essential molecules, such as oxygen and glucose, while expelling waste products. This passive transport mechanism does not require energy, making it an efficient way for substances to move across cell membranes.