Jeff Horwitz first connected with Frances Haugen late last year when he was trying to meet more sources at Facebook. He eventually earned her trust and access to a trove of internal research from the company. Horwitz tells Brian Stelter what his source relationship was like; why he wondered if anyone would care about the revelations; and whether he is working on any more Facebook Files stories. Plus, Stelter asks about Horwitz's headband fashion statement. 

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