EXCLUSIVE: Jessica Biel Discovers Her Ancestors Were Jewish on 'Who Do You Think You Are?' -- Watch!

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Jessica Biel gets a big surprise on this week's episode of Who Do You Think You Are?.

The 35-year-old actress joined the uber popular TLC series to debunk several stories of her family's history, and only ET has an exclusive sneak peek.

WATCH: Courteney Cox Uncovers Shocking Royal Family Drama in 'Who Do You Think You Are?' Premiere

In the preview clip, Biel is shocked to find out that her ancestors were Jewish.

"Wow, I've never heard of this before in my family," Biel says. "That's kind of a big deal to not know about."

"That sort of changes everything," she adds.

EXCLUSIVE: Julie Bowen Learns Her Ancestors Fought to End Slavery on 'Who Do You Think You Are?' -- Watch!

This season, the show will also follow Julie Bowen, Courteney Cox, Jennifer Grey, Smokey Robinson, John Stamos, Noah Wyle and Liv Tyler.

Watch the exclusive clip above.

Who Do You Think You Are?
airs Sunday at 10 p.m. ET/PT, 9 p.m. CT on TLC.