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Jessica Biel opens up on motherhood in her first post-baby interview after giving birth to son Silas, her first child with husband Justin Timberlake, in April. "Probably the moment he wakes up from a nap," the new mom tells E! News about her favorite part of caring for her little boy.

"He's sort of looking around and you sort of creep up and look over the crib and he looks up and he goes [Biel lets out a big sighing sound]. Just a gummy mouth, no teeth, just a big smile, happy that you're alive and you're just looking at him. That's probably the most magical," she explains.

The "Total Recall" actress then jokingly adds, "But you quickly move on from it because there is a dirty diaper in your palm."

Jessica's brother, Justin Biel, says motherhood has given her a "new level of confidence" and "calm." Justin who did interview with her during a party celebrating the latest collection of Bare bags tells PEOPLE, "As a mother she is just so in her element, and so centered, and I think it has a lot to do with that."

"It's an amazing thing, and it's amazing to see Jessica become a mom, and I'm the closest uncle, and it's an amazing opportunity for them, and I'm so excited for them," he gushes. "I'm just thrilled to get to know the little guy as he grows up."