The Kremlin and President Donald Trump have each denied allegations that Russia and the Trump campaign colluded in the 2016 presidential election – but the probe into Russia’s meddling is forging ahead.

The announcement in early August that Special Counsel Robert Mueller has impaneled a grand jury as part of his examination is widely seen as an indicator that his investigation is entering a new phase.

From the firing of the nation’s F.B.I. director to Trump’s oldest son’s meeting with a controversial Russian lawyer, here’s what you need to know about the Russian investigation so far.

Early problems

Before Trump ever took office, tens of thousands of emails from the Democratic National Committee and other officials connected to former Democratic presidential nominee Hillary Clinton were leaked.

Those emails – released in July 2016 ahead of the Democratic National Convention – purportedly showed the party favoring Clinton over Vermont Sen. Bernie Sanders and led to the resignation of party chair Rep. Debbie Wasserman Schultz.

But more than just ousting Wasserman Schultz, intelligence officials concluded that those responsible for leaking the emails were connected to the Russian government. In its assessment of the hack, the CIA concluded that Russia intervened in the election in order to help Trump secure the presidency.

MUELLER’S RUSSIA PROBE: WHAT TO KNOW

Before he handed over the White House to Trump, former President Barack Obama sanctioned Russia for its alleged involvement in the election – a move that would eventually come back to dismantle one of Trump’s senior aides.

Trump’s oldest son, Donald Trump Jr., also got the administration into hot water for his own actions during the campaign.

Trump Jr. confirmed in July 2017 that he took a meeting with a Russian lawyer during the campaign as she was supposed to have damaging information about Clinton.

“This is obviously very high level and sensitive information but is part of Russia and its government’s support for Mr. Trump,” an email about the meeting said in part.

Trump Jr. maintained that the lawyer, Natalia Veselnitskaya, did not have any information to share and instead wanted to discuss other matters.

TRUMP JR., MANAFORT SLATED TO APPEAR BEFORE SENATE PANEL HANDLING RUSSIAN INVESTIGATION

Paul Manafort, Trump’s former campaign manager, and Jared Kushner, the president’s son-in-law, were at the meeting as well. The two are also being investigated.

Flynn’s fall

Michael Flynn’s tenure as Trump’s national security adviser was short but rife with controversy that still bedevils the administration. But Flynn didn’t come without a warning.

Only a few days after the November election, Obama met with Trump to share his concerns about Flynn, a retired lieutenant general. Flynn had served under Obama as head of military intelligence until he was fired in 2014 following reports of insubordination and questionable management style.

Still, Trump ignored Obama’s apparent apprehensions and selected Flynn as his national security advisor. Not a month later, Trump accepted Flynn’s resignation.

HOW IS JARED KUSHNER LINKED TO RUSSIAN INVESTIGATION?

As Obama issued the sanctions on Russia for its involvement in the election, Flynn reportedly called the Russian ambassador to discuss the move. Flynn initially denied speaking to the ambassador, but when intelligence officials revealed proof, he said he just didn’t remember speaking on that topic.

Flynn resigned under harsh scrutiny for misleading the administration, including Vice President Mike Pence, about his ties to and conversations with Russian officials.

He remains under multiple investigations by congressional committees and the Pentagon’s inspector general. Mueller has included Flynn in his probe, and his investigators are trying to determine if he was secretly paid by the Turkish government during the campaign, the New York Times reported in August.

Flynn registered as a foreign agent with the Justice Department in March 2017.

Firing the FBI director

Trump sacked F.B.I. Director James Comey on May 9 – less than two months after Comey publicly proclaimed that the agency was investigating ties between Russia and Trump’s campaign.

The White House maintained that Comey was relieved from his duties due to his handling of the investigation into Clinton’s use of a private email server during her tenure of secretary of state. But days later, Trump alluded that he had considered the Russian investigation when he fired Comey. 

RUSSIAN AMBASSADOR SERGEI KISLYAK, AT CENTER OF ELECTION CONTROVERSY, CONCLUDES ASSIGNMENT

Comey told a Senate intelligence committee in June that he was concerned about the “shifting explanations” that came from the White House regarding his firing.

He also claimed that Trump had asked for the F.B.I. to drop its investigation into Flynn during a February meeting. The White House has denied that Trump was attempting to influence the F.B.I. director.

Before the committee, Comey confirmed that as well that he had reassured Trump repeatedly that he was not under investigation by the F.B.I.

Russians in the Oval

In the wake of Comey’s dismissal, the Trump administration was rocked with reports of the president’s own controversial dealings with Russian officials in the Oval Office.

The Washington Post reported on May 15 that Trump shared classified information regarding ISIS threats with Russian Foreign Minister Sergei Lavrov and Sergey Kislyak, the Russian ambassador at the time. The information was reportedly given to the U.S. from Israel and not meant to be shared.

Later that week, the New York Times reported that Trump told those officials the day after firing Comey – who he allegedly called a “nut job” – that the personnel change took “great pressure” off of him.

Special counsel called

The Department of Justice announced the appointment of former F.B.I. Director Robert Mueller as special counsel to oversee the federal investigation into Russia’s alleged influence on the election on May 17.

The appointment followed a growing Democratic outcry for someone outside the Justice Department to handle the probe.

TRUMP SAYS SESSIONS ‘SHOULD NEVER HAVE RECUSED HIMSELF’ FROM RUSSIA INVESTIGATION

Mueller was given wide berth to carry out his investigation, and he expanded the probe to look into whether Trump obstructed justice with Comey’s firing.

Trump has criticized Mueller’s friendship with Comey as “very bothersome.” The two were former colleagues at the Justice Department.

Mueller has reportedly impaneled a grand jury to continue the investigation. A grand jury gives prosecutors the ability to subpoena documents and gather on-the-record witness testimonies. It doesn’t necessarily mean criminal charges will be sought.

Trump faces Putin

Trump finally met with Putin for the first time face-to-face at the G-20 summit in June.

He immediately pressed his Russian counterpart on the allegations of election meddling – which Putin denied, according to Secretary of State Rex Tillerson.

KELLYANNE CONWAY ON COLLUSION: ‘WHAT’S THE CONCLUSION?’

Lavrov told reporters after the meeting that Trump had accepted Putin’s assurances that Moscow was innocent of interfering in the election.

Anyone else under investigation?

Manafort resigned as Trump’s campaign manager in August 2016 amid questions regarding his business dealings in Ukraine.

The special counsel has taken over a criminal investigation into Manafort’s financial dealings, which began even before the 2016 election, according to The Associated Press. F.B.I. agents raided Manafort’s Virginia home in July, taking with them documents related to the Russia investigation. 

Manafort has been the subject of multiple investigations into his financial dealings and lobbying work. He has denied any colluding with Russia.

TRUMP’S FBI PICK SAYS HE’LL FOCUS ON THE LAW, NOT POLITICS

In June 2017, Manafort officially registered as a foreign agent for work he did with a Ukrainian political party from 2012 to 2014.

Kushner, too, has been under F.B.I. scrutiny.

Kushner, married to Trump’s daughter Ivanka, may possess substantial information relevant to the Russian investigation, officials told NBC in May.

He also held private meetings with lawmakers regarding the controversial meeting Trump Jr. set up with the Russian lawyer. Rep. Mike Conaway, R-Texas, who is leading the House intelligence committee’s probe into Russia’s involvement in the election, said Kushner was “straightforward, forthcoming [and] wanted to answer every question we had.”

Kushner has denied colluding with Russia or knowing anyone who did so.

The Associated Press contributed to this report.