Oprah Winfrey will air her interview with the Kardashian family on Sunday, and the famed talk show host indicated on Facebook that she dug deep.

"This interview I'd say was another level of forthrightness and honesty," she wrote, adding that she questioned Kim Kardashian about her 72-day marriage to basketball player Kris Humphries.

"Why did she leave after 72 days? Her answer leveled me," Winfrey wrote.

To prepare for their talk, which will air on OWN Sunday, Winfrey said she "did a full-on Kardashian Kram."

"I had never met them, nor seen the show," she admitted of one of TV's most famous reality show families.

It's a good thing she did her homework because Winfrey said she spent a lot of time on set with Kim, Kourtney, Khloe and the rest of the family.

It was the "longest interviewing session I can ever recall, talking to ALLLLLLLL the Kardashians," quipped Winfrey. Still, she implied, it was worth it.

"I genuinely wanted to know why they have become a cultural phenomenon," she added. "Why do so many people love to watch their every move and why do so many others love to hate them. Are they completely ego centered? Are they really 'famous for being famous' or is there something more?"

"Oprah's Next Chapter" featuring the Kardashians airs this Sunday at 8 p.m. on OWN.