What does not expand in a cell when diffusion takes place?

During diffusion, substances such as gases or solutes move from areas of higher concentration to areas of lower concentration, but the cell's volume typically remains constant. This is because diffusion involves the movement of molecules rather than the expansion of the cell itself. The cell membrane regulates the flow of substances, ensuring that the internal environment remains stable without expanding. Therefore, the cell's structural integrity is maintained while diffusion occurs.