How can God have a personal relationship with every human?

I'm a weak agnostic (and only 17, so don't expect much intellectually). To a certain extent, I believe in God because of the world around me--it's just this inherent feeling that it has a purpose (I know that this "argument from design" has flaws. The philosopher David Hume destroys its logic in "The Dialogs"). However, what I cannot comprehend is that God has a personal relationship with all 7 billion humans.