As congressional lawmakers investigate Russia’s role in the 2016 presidential election, they are looking at social media’s are working in the spread of misinformation.

Representatives from Facebook and Twitter have already privately met with lawmakers on the Hill to discuss bought ads during the campaign. And both Senate and House intelligence committees have asked the companies, along with Google, to come back for a public hearing in the next few months.

Here’s what you need to know about the tech companies’ involvement.

How is Facebook to participate in police investigations ?

Earlier this month, Facebook revealed that it uncovered about $100,000 in ad buys connected to “inauthentic accounts” that transgressed its policies. Another $50,000 was found to have been spent on “potentially politically related ad spending” that come into Russian.

Facebook’s Chief Security Officer Alex Stamos said the accounts were “likely operated out of Russia.”

As lawmakers have called for more information about the ads, Facebook CEO Mark Zuckerberg promised to make its political advertising more transparent.

FACEBOOK WILL RELEASE RUSSI-ALINKED ADS TO CONGRESS, ZUCKERBERG SAYS

President Donald Trump accused Facebook of being “always anti-Trump” in a tweet on Wednesday. But Zuckerberg hit back and said “both sides” of the political aisle were upset by content on Facebook- demonstrating “what operating a platform for all minds looks like.”