Amid the investigative and research questions over the past several years, there was always a question about who, within the Trump orbit, may have been subject to FISA court authorized surveillance during their activity in 2016.
Because they were initially the four targets of the FBI investigation, there was speculation Paul Manafort, George Papadopoulos and/or Lt. General Michael Flynn were also subjects of Title-1 FISA Court authorized surveillance, in addition to Carter Page.
Today during his testimony, Inspector General Michael Horowitz specifically noted there was no other FISA application against any other campaign official. [See 05:23 of testimony to questions by Senator Chris Coons – prompted just hit play]:

“The only FISA we found existed was the one we have written about here as to Carter Page”…

That means all other FBI investigative evidence documented against Manafort, Papadopoulos, or Flynn had to come from some other method of surveillance.
This begs a significant question….
Carter Page was not associated with the campaign or transition after the election, so under what authority did the DOJ allow the Mueller team to gain access to all of the Trump transition emails, texts, electronic and phone communications? 

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….Maybe a good question for Rod Rosenstein?
Then again, perhaps this speaks to why the DOJ is hiding the scope memos…
I digress.