How does diffusion affects cells?

Diffusion is a common way for cells to move particles through their membranes. Basically, particles want to move from an area of high concentration to an area of lower concentration. For example, if a dehydrated cell is put into water, the water molecules around the cell will move through the cell's membrane and balance out with the cell. When it is only water being diffused, the process is called osmosis. Also, cell membranes are selectively permeable, which means some things are just too big to fit through.