Here's who has been charged so far in Mueller's Russia probe

Since taking over the investigation, Mueller's team has charged four Americans once affiliated with the Trump campaign or administration, and 13 Russians and three Russian companies involved in US election interference.

Paul Manafort, former Trump campaign chairman

Former Trump campaign chairman Paul Manafort surrendered to federal authorities on October 30, 2017, after he was indicted, along with his business associate Rick Gates, on 12 counts, including conspiracy against the US and money laundering.

Manafort, who pleaded not guilty, had been

Manafort was forced to step down as Trump's campaign chairman in May 2016 after coming under fire for his connections to Russian oligarchs and his past lobbying efforts abroad.

Rick Gates, one of Manafort's business partners

In October, Gates was indicted along with Manafort on 12 counts, including conspiracy against the US, making false statements, and failing to file reports of foreign bank and financial accounts. He pleaded not guilty on all counts.

Gates joined Trump election efforts in the spring of 2016, working as Manafort's deputy. He traveled with Trump and grew close with many top campaign officials.

After Manafort was ousted as Trump's campaign chief in August 2016, Gates continued working on behalf of the soon-to-be president, helping fundraise $25 million for the pro-Trump nonprofit America First Policies and working on Trump's inaugural committee. As Mueller's probe intensified in the early months of the Trump administration, Gatesleft the nonprofitaltogether.

But as recently as June,The Daily Beast reportedthat Gates was still visiting the White House and working under Tom Barrack, who has remained one of Trump's most trusted advisers.

George Papadopoulos, a former Trump campaign adviser

On the same day Mueller's office announced the indictments of Manafort and Gates, it was revealed that George Papadopoulos, a 30-year-old former Trump adviser, had pleaded guilty to lying to the FBI about his contacts with Russia.

According to documents that were unsealed by the Mueller investigation, Papadopoulos had made at least six attempts to set up a meeting between the Trump campaign and Russian representatives throughout the course of the 2016 presidential campaign, using a London-based professor named Joseph Mifsud and a female Russian national as conduits.

He was arrested October 5, 2017, and subsequently cooperated with Mueller's team.

Trump has described Papadopoulos as a low-level volunteer.

"Few people knew the young, low level volunteer named George, who has already proven to be a liar," Trump tweeted following news of the guilty plea. "Check the DEMS!"

Michael Flynn, Trump's former national security adviser

Flynn, who has reportedly been at the center of Mueller's investigation for months, is perhaps the most high-profile person to be indicted to date. On December 1, 2017, he pleaded guilty to lying to the FBI about

13 Russian nationals and three Russian companies

On February 16, Deputy Attorney General Rod Rosenstein announced the indictments of 13 Russian citizens and three companies allegedly involved in meddling in the US political system.

"The defendants allegedly conducted what they called 'information warfare against the United States' with the stated goal of spreading distrust towards the candidates and the political system in general," Rosenstein said.

The charges focused on the Internet Research Agency (IRA), a notorious Russian "troll factory" that focused on sowing political discord during the 2016 US election by using internet bots to spread fake news and pro-Donald Trump propaganda on Facebook, Twitter, and other social media platforms.

Yevgeny Prigozhin, a prominent businessman and associate of President Vladimir Putin who helped fund the IRA, was charged along with two of his businesses.

The defendants included 12 other Russian citizens, all of whom were identified as former IRA employees who played a role in Russian influence operations before, during, and after the 2016 election.

They are: Mikhail Bystrov, Mikhail Burchik, Aleksandra Krylova, Sergey Polozov, Anna Bogacheva, Maria Bovda, Robert Bovda, Dzheykhun Aslanov, Vadim Podkopaev, Gleb Vasilchenko, Irina Kaverzina, and Vladimir Venkov.