It is from Crash Course Chemistry. It is at 1 minute and 44 second. Here it goes:
It is what we use to translate from the very small to the very big, to parley the stuff that we cannot see into the stuff we can.
I have looked up what parley means in a buch of dictionaries, but I cannot get what it means there.
In wikdtionary parley is defined as
(intransitive) To have a discussion, especially one between enemies.
But that doesn't seem to fit this context.