Christians claim God is omnipresent: Everywhere. For this to be true, God has to exist within every elementary particle throughout all of the near infinite galaxies we have discovered; in addition to existing between them.
However, it is believed by Christians that God created everything. If God is confined to the realm of matter and motion, and is an incredibly small particle that forms together to create the universe, then we are just a bit of God.
Lastly, Christians believe God is super-natural, above matter and motion (its creator), but found throughout it. The particle explanation only serves to illustrate the pervasiveness of an omnipresent entity, but it isn't the omnipresent entity; just its form.