Meet David Muir, the Man Taking Over ABC's 'World News'


David Muir is already moved into his ABC World News office and he invited ET as his first guest.

When Diane Sawyer says goodbye to the news program tonight after five years, Muir is the man taking over.

"[I'm] humbled to follow in the footsteps of Peter Jennings, Charlie Gibson and Diane Sawyer, who's not only a dear friend of mine but a force," Muir told ET's Brooke Anderson. "What a gift for me."

At 40 years old, Muir will be America's youngest evening news anchor in nearly half a century. His youthfulness could work in his favor in terms of engaging more tech savvy viewers. Muir told us that he'll be Tweeting during commercial breaks.

Muir makes his big debut on September 2. Watch the video for an early clip of Muir anchoring at Ithaca College.