The illusion of a "solid surface" is a perceptual result of electrostatic repulsion. Atoms consist of a dense nucleus surrounded by clouds of negatively charged electrons. When the electron clouds rapidly orbiting the nuclei of different atoms approach one another, an electromagnetic repulsive force (electrostatic repulsion) comes into play. This electromagnetic repulsion causes the overlapping electron clouds to push against each other. This resistance between the overlapping electron clouds imparts volume and structural integrity to matter, thereby giving objects a solid feel. This demonstrates that what appears to be solid matter is, in reality, merely forces and empty space.