Credit: Humberto Carreno/

Kim Kardashian let it all hang out in NYC on Tuesday.

Heading in for an appearance on The Late Show with David Letterman, Kardashian, 30, wasn't afraid to reveal some serious cleavage in tight black Marc Bouwer dress with a transparent panel on the top.

In related news, Kim got a little grossed out by sister Kourtney's boob talk on Twitter.

"What a flight!" Kourtney, 31, Tweeted. "Kim slept next 2 me while my boob was about to explode w breast milk! I went to the bathroomsqueezed."

Her sister's retort? "TMI"