What Is the First Unit of Discourse?

Foucault says the statement is not the atomic first building block of, or like, smallest building block of history. So he goes through the different other theories of what the first or smallest unit of discourse could be and why each of them is insufficient. But I think in the fact that he's acknowledging that, he sees how his description is, he might make you think that. The meaning that can come out of the statement is very much of its own right.