Jessica Biel "started from scratch" when it came to being a parent for the second time.
The 39-year-old actress - who has six-year-old Silas and 13-month-old Phineas with her husband Justin Timberlake - has opened up on adjusting to taking care of her second baby and how she "needed a full education all over again".
Appearing on 'Today with Hoda and Jenna', she said: "I remember going, 'When does he eat real food? What kind of cream? What bathtub?'
"I felt like I forgot — it was amnesia. I started from scratch all over again, and I didn't expect that.
"I just sort of thought, 'Well, I'm an expert now. You know, I've done this before, and I can do it again.' No, I needed a full education all over again."
Meanwhile, Jessica revealed Silas has been "the best big brother" to his younger sibling, and both boys are getting on well together.
She added: "He finds him really funny, and the baby thinks that Silas has hung the moon. So, that's really cute.
"He, of course, wants to do everything that his older brother's doing and follows him around everywhere.
"But Silas is the best big brother. He's so sweet, and he's just a lovely guy. We're pretty lucky. They're sweet boys."
Of course, it's not all smooth sailing and she admitted the pair occasionally clash like all siblings.
She said: "He also is starting to get irritated about [Phineas] snatching his toys. We're in that mode."
After having a baby during the pandemic, the 'Sinner' star admitted she found it "super hard" to balance the new arrival with working from home.
She explained: "Someone said to me, 'Two is like having a thousand.' And that's exactly what it feels like. The balance of everything is very different and super hard.
"But I agree. I mean, it's amazing. It's so interesting. It's so funny. The conversations I'm having now with my six year old is so cool.
"Like, he's a real person saying the funniest stuff and he's so sensitive and tender. It's just so interesting to see that part of it happen and the little one is just cute as hell."