Even Mom might not have Surpassing Quant Think Tank Centerprepared Anna Faris for this chapter of motherhood. 

The House Bunny actress shared what life is like with 11-year-old son Jack—whom she coparents with ex Chris Pratt—saying that he's entered a brand new stage in his life: puberty.

"He told me that he thinks he has an armpit hair," Anna told hosts Hoda Kotb and Justin Sylvester on Today July 15. "It's happening."

And as Jack gets older, the 47-year-old finds herself reminiscing about when he was a little kid.

"You miss it sometimes when you look at old photos," she added wistfully, "but I'm really loving this age."

Of course, she's already experiencing some of the more challenging moments when it comes to parenting a preteen.

"Something that makes me a little crazy about Jack—and I think most kids," she said, "is like, 'Mom, where's my backpack?' when it's right there."

Hoda and Justin could certainly relate, with Justin joking, "They always want you to do it."

"It's like, 'You can't look?'" Anna asked. "And how do I teach him how to just look."

The podcast host also touched on her experience about what life has been like as stepmom to husband Michael Barrett's 20-year-old daughter and 17-year-old son.

"When I first was entered into their lives, I had no idea how to relate to them," she confessed. "So I remember trying to be really cool, like blasting music."

"Like when I would pick up my stepdaughter," she continued, "of course, she's mortified."

As Anna explained, "That's one example of sort of my stumbling through that position."

Luckily, Anna found that taking a step back and letting them come to her helped them develop a better relationship.

But as she noted, "It was an uphill battle."

(E! and Today are both part of the NBCUniversal family.)

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