Are you referring to the Strong-Nuclear Force? This is responsible for binding quarks together to make hadrons. This force acts between neutrons and protons and explains how atomic nuclei hold together and overcome the electrical repulsion of the protons.<br />
Or you may also be referring to quantum fluctuations that seem to be seething down at the planck scale that would still be there if you had a box with absolutely nothing in it; no atoms, no photons, no neutrino's...NOTHING. You would still have a Zero Point Field energy there that we have yet to understand.
Hey...show off...I admire ;}
The energy of an atom is bound up in the energies that hold its constituent particles together.
The Ganesh ( God ) Particle through the Shiva Stargates