The reach of Russia's misinformation campaign during the 2016 US election was substantial. Recode reports Facebook will tell a Senate committee that 126 million users in the US saw posts, stores, or other content from Russia-linked groups. The social network has only publicly stated Russia's ads were able to reach 10 million.
Not all of the content in Russia's overall campaign appears to have been directly Election-related, but much of it was. It's believed Russian trolls used sites like Facebook to fuel political disagreements and to increase the likelihood of Donald Trump winning the presidency.
Facebook, Google, and Twitter will speak with congressional investigators this week.