Jennifer Garner was on Tuesday’s episode of The Tonight Show with Jimmy Fallon, and she gave Jimmy some good warnings.

Among Jennifer Garner’s heads-up moments was when she advised him to take pictures of his daughter Winnie, almost 2, being sweet to his newborn daughter, Francis.

Because they grow up and do battle. Such truth from Jennifer Garner, who has 3 kids, daughter Violet, 9, daughter Seraphina, 6, and son Sam, 3, with her husband Ben Affleck.

“How’s your oldest so far?” Jennifer Garner asked, wanting to know how she gets along with the baby.

Jimmy Fallon said of his daughters, whom he shares with his wife of seven years, Nancy Juvonen, “She’s good, she loves the little one, and like, kisses her every day.”

“She does?” Jennifer Garner said, a little surprised.

She continued, “Enjoy that. Take pictures, yes. No, I mean, they just have their, you know, they have their moments… You’re driving to school and you kind of hear a yelp. You look in the rearview mirror and there’s just like a pinch happening — a pinch for the ages.”

Jennifer Garner also warned Jimmy Fallon about the many evil plans that clever kids can hatch in order to get what they want from their parents.

“The other thing is that they can get clever,” Jennifer Garner said.

She added, “They’re all gonna go nuts when there’s a new baby, right? One way or another, if it isn’t now, it’s going to be later. It’s coming.”

Jennifer Garner went on to tell a hilarious story about her daughter and getting duped.

She said, “We had one who wanted to still be the baby, but she never wanted to say, ‘I want to still be the baby. She wanted to be carried everywhere. What she was telling us was that she was a mermaid. She had a tail and she had flippers and she needed to be carried everywhere, and we bought it.”

She added, “Suddenly I’m lugging this huge kid around and I saw her smiling to herself, smirking… We would get to a staircase and she’d say, ‘Oh my tail, what with my flippers, I can’t make it up that staircase.'”

Jennifer Garner’s last bit of advice for the new dad?

She said, “They’re smarter than you are so just be ready for that.”

What do you think of Jennifer Garner’s parenting advice to Jimmy Fallon?