[HIGHLIGHTS] After the arrest of the leaker of the Pentagon documents. Who can see America's secrets?

The Pentagon document leak crisis has raised several questions about who can access classified documents in the United States. Hundreds, perhaps thousands, of government employees likely have security clearances that would give them access to those documents.

There are about two million Americans who have access to classified documents. The U.S. government generally divides its sensitive official documents, information, and reports into 3 levels, as follows: Top Secret, Top Secret and Secret. The CIA Director stressed that Americans should learn a lesson on how to tighten security on such documents.