The technique is usually used to image molecules, by measuring attractive forces between the tip and sample, or the electric currents that pass between them. (scientificamerican.com)
At the point on the ocean's surface closest to the moon (point A in the illustration), the lunar gravitational attractive force is strongest and it pulls the ocean toward itself. (scientificamerican.com)
When it is very cold, the gentle vibrations can push electrons together, producing a net attractive force that drives them to pair up. (newscientist.com)