Anthony Fauci stopped by the Late Show With Stephen Colbert to discuss his new memoir.

Fauci, who became a national celebrity during the Covid-19 pandemic in his role as the director of the National Institute of Allergy and Infectious Diseases, published On Call: A Doctor’s Journey in Public Service with Viking on Tuesday. The press says his book is “an inspiration for readers who admire and are grateful to him and for those who want to emulate him in public service.”

Colbert noted that Fauci’s book has a chapter about former President Donald Trump—with whom Fauci had a famously mercurial relationship—titled “He Loves Me, He Loves Me Not.”

“I’m pretty sure I know where that one landed,” Colbert joked.

“I had a very complicated relationship with President Trump,” Fauci said. “In the very beginning, we got along very well. I write in the book, I don’t know whether it’s because [we’re] two guys from New York—him from Queens, me from Brooklyn—that we kind of understood each other and we got along very, very well early on. It was only when [he] began to say, because he wanted so much for this thing to go away, that he was saying things that were incorrect.”

Fauci said that Trump’s staff began doing opposition research into him after he contradicted some of Trump’s incorrect claims about the pandemic.

“I became anathema, persona non grata,” he said. “It was most unusual. I was working in the White House, and the communications people in the White House were doing opposition research…telling the public about how I’m usually wrong in what I say. That’s sort of, like, weird.”

Michael Schaub is a contributing writer.