In the body, water moves through semi-permeable membranes of cells and from one compartment of the body to another by a process called osmosis. Osmosis is basically the diffusion of water from regions of higher concentrated regions to regions of lower concentration along an osmotic gradient across a semi-0permeable membrane. As a result, water will move in and out of tissues and cells depending on the relative concentration of the water and the solutes found there. Appropriate balance of solutes inside and outside of cells must be maintained to ensure normal function.