Osmosis is the diffusion of water. This pendulum represents the passing of a water molecule through a membrane at osmotic equilibrium. Osmosis continues to happen as the molecule of water passes back and forth through the membrane represented by the cone on the back of the pendulum. The membrane also contains aquaporins, which is the part of the membrane responsible for the passage of water. Without the presence of aquaporins water could not pass through the membrane in both directions which means osmosis would not be possible. The stones on the base represent concentrations. The darker the stones the more concentrated with water it is. Since osmosis works down the gradient from high to low concentrations the pendulum representing the water molecule, swings back and forth between the the two areas of concentration traveling from an area of high concentration to an area of low concentration. This will happen continuously at osmotic equilibrium.