The Trump administration made the unprecedented move of revoking former CIA Director John Brennan's security clearance on Wednesday.

The White House has also threatened to revoke the clearances of nine other former intelligence officials — all of whom have publicly criticized President Donald Trump.

Here's a look at who they are and what they've said to criticize Trump.

President Donald Trump stunned the nation on Wednesday with the announcement that he revoked the security clearance of the former CIA Director John Brennan over his criticism of Trump and the administration. The White House described Brennan's actions as "erratic conduct and behavior."

Trump's move earned some sharp reactions in Congress and within the national-security community, with some saying they perceived it as an abuse of presidential power.

As national security experts have explained, it's standard protocol for former high-level intelligence officials to keep their security clearances after their government service has ended, so they can be a resource to future administrations on matters of national security.

Despite the outrage over Trump's action on Brennan this week, the president might not stop there. The White House has publicly named nine other former national security and intelligence officials who have publicly criticized the Trump administration.

Here is a snapshot of the nine officials and what they've said: