 Cohesion is the tendency of molecules of the same type to stick together. Water molecules are highly cohesive. This cohesion is what allows water molecules to move against gravity. As you can see in this animation, as one water molecule evaporates, it pulls along a chain of molecules sticking together via cohesion, illustrated here by the molecules holding hands. This draws water up from the roots, through the trunk, and out the branches to leaves, moving against the force of gravity.