4:11 p.m. ET: "Nightline" senior producer Melinda Arons tweets:

Mark Zuckerberg banging the traditional Facebook gong to ring in #facebooksearch. See more on @ nightline 2nite. twitter.com/MelindaNTL/sta…

- Melinda Arons (@MelindaNTL) January 15, 2013

Credit: MelindaNTL/Twitter

3:18 p.m. ET: Get a better feel for Facebook's new Graph Search tool IN PHOTOS:

Credit: Facebook

See the full slideshow HERE

1:33 p.m. ET: EXCLUSIVE: How you search Facebook is about to change. In fact, just the act of searching Facebook is probably about to start.

Facebook is trying to give Google a run for its money, with a new product called "Graph Search." It turns some of the personal information people have shared on Facebook into a powerful searchable database.

Read more HERE

Credit: Facebook

Facebook allowed ABC News "Nightline" behind the scenes ahead of today's product launch, an event shrouded in secrecy and rife with speculation. Watch the full story TONIGHT at 12:35 a.m. ET

12:09 p.m. ET: PLAY CATCH UP: Last night, "Nightline" went on the frontlines of a city in crisis. Boston has suffered a raging flu epidemic and "Nightline" spent the last 48 hours documenting patients who already have it, those who are taking measures to avoid it and the doctors who are battling the outbreak. Watch what happens HERE:

10:04 a.m. ET: BREAKING: Oprah Winfrey said today that disgraced cyclist Lance Armstrong came well prepared for their highly anticipated interview, although he "did not come clean in the manner [she] expected."

Credit: George Burns/Harpo Studios, Inc.

Read the full story HERE and follow ABC's Neal Karlinsky on Twitter @NealKarlinsky for the latest updates