How does dust get under the cell phone screen?

I don't quite understand it. There's that space between the outer screen and the inner screen and there's absolutely no doubt about it... dust will find its way in there in time. Where is the crack in the cell phone that lets in all that dust? I have no idea. It's just one of those mysteries in life, like where did the pair to this sock go? and how come my suitcase doesn't close when it did when I got here? and how do boogers form? It's a strange strange world out there.