personal information. >> joining us now to explain all this is cnn senior media correspondent brian stelter. brian, i think we first need you to kind of explain what the relationships are here, because a lot of nuances. >> yes. this is a story on the front page of the morning paper. it says something to the effect of a firm that helped the trump campaign exploited facebook data. what does that mean? it starts well before president trump entered the race in 2015. there was a researcher, a professor who went ahead and harvested facebook profiles. a couple hundred thousand people's data was taken by this personality quiz you could fill out. re remember seeing these on facebook a few years ago? you would have to fill on you a few questions and tell you more about yourself. one of the quizzes was a way to get data from users. not just your own data but your friend's data as well. ls all of a sudden this professor had 50 million facebook profiles