Diffusion is an essential process for the functioning of cells, as it allows for the exchange of materials and energy between the cell and its environment. Diffusion occurs when molecules move from an area of higher concentration to an area of lower concentration. This process occurs within the cell membrane, as molecules of solutes move across the membrane as well as through the membrane. Diffusion is important for the transport of substances across cells, which is necessary for metabolic processes and other essential functions. Diffusion is an important process that helps cells to maintain homeostasis.