We have a low potential. And as soon as we let go, this marker moves down its gravitational potential gradient. And we have to expend absolutely no energy in moving this marker in the same exact way cholesterol and water will move down our electrochemical gradient. And we will have to use no source of energy for this type of movement. This is known as passive diffusion because we are not using energy and we are not using any type of transport protein, integral protein. Now, water is such a common molecule that undergoes path of diffusion that we give it a special type of name.