Jessica Biel Says Son Silas, 9, Is Aware His 'Body's Changing': 'We're Talking About Deodorant'

Biel shares her sons Silas and Phineas with husband Justin Timberlake

Jessica Biel's son knows his body will soon start to look and feel a little bit different.

On Wednesday, May 22, the actress, 42, appeared on SiriusXM's Let's Talk Off Camera with Kelly Ripa and spoke about her new book A Kids Book About Periods. Biel, who shares her two sons Silas, 9, and Phineas, 3, with husband Justin Timberlake, 43, noted that she's already been having conversations with her older son about puberty.

"We talk a lot about that already," Biel says of discussing puberty with her son. "We're all, as parents, I think building it up in our brains as to how our children are gonna react and I do feel like we don't give them enough credit for just kind of being able to understand and absorb it and then move on."

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Related: Jessica Biel Reveals 9-Year-Old Son’s Reaction After Reading Her Book About Periods: ‘He Was So Cool About It’ (Exclusive)

"They're just so in the present moment. It's amazing how these kids do this, but we talk about a ton of other things. I mean, I've definitely told him, 'Hey, I'm not feeling great today. I'm on my period and I'm just really, I'm not really that patient so I need you guys to be my best partners and best-listening ears today.'"

"We had that conversation, but we talk a lot about his body's changing a lot and he's experiencing that. He's experiencing growing pains. He has a hard time sleeping," the mom of two continues. "He'll be waking up in the middle of the night. His legs hurt. His back hurts."

Adding that her son has gone from a little guy to almost a preteen, Biel says that she and Timberlake have noticed that Silas looks a little different.

"He's just growing. It's so amazing, so we talk a lot about that. We're talking deodorant. We're talking about hormones in our bodies and why we smell a different way, and so we're into it and we're on the precipice of all the big conversations I think."

Earlier this month, Biel spoke with PEOPLE about her new book, noting that she and Silas had read the book for the first time together recently.

"My son and I read half of the book for the first time this morning, it was really cool to see him listening," Biel told PEOPLE. "He would read a page and I would say, 'Okay, so this is what's happening.' And I said, 'Okay, this is the period. This happens to me every month. And it'll happen to people in school.' "

"This was... The best part, is he kind of was like, 'Oh, that's weird.' I said, 'Yeah, it is kind of weird, but trust me, it's weird for me too. When it happens to me, it's still weird.'"

"And I said, 'Think about it. There's somebody at school that might have their period and they might need your help or support someday, and it's really going to be important for you to understand what's happening so you can help a friend if they need something,'" Biel concluded.

Ultimately, Biel said she wants her sons to understand that when it comes to menstruation, there's only "one option."

"The option is to be compassionate and not be freaked out and support," she said. "I got a piece of it in, but I could see the wheels in his brain kind of turning over, and he was so cool about it."

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