Jessica Simpson's son is growing up!

J. Webber / Splash News

In a new Instagram post, Jessica shared a photo of her 4-year-old son Ace Knute's first haircut. He had been rocking long blond locks like his pop star mom up until his first trip to the salon.

And yes, we mean salon. When your mom is Jessica Simpson, not just any stylist or barbershop will do for your first haircut, it has to be a person your mom trusts with her incredible locks.

In the Instagram caption Jessica thanked one of her hairstylists, Jessie Holiday, for "making my stud look all grown up" and added a crying emoji.

Jessica's kids are certainly growing up quickly. Her 5-year-old, Maxwell Drew, started kindergarten last month, showing off her first day outfit, a plaid dress and matching headband, on her mom's Instagram. And Ace is already excelling at homework, practicing writing numbers over the summer before he started pre-school.

Her youngest kept her busy this summer, with Jessica throwing Ace a "Moana"-themed birthday party that would make any fan of the Disney movie jealous. Ace's party included appearances from Moana and Maui and giant pineapple toy bags, personalized for all of the guests.

The 37-year-old loves being a mom, but is content with her family of four, telling Ellen earlier this year that she has an IUD to keep her from getting pregnant. "I have two beautiful children, and I'm not having a third," she said.

That might have something to do with the fact that her husband, Eric Johnson, has been regularly pampering her in the same, amazing way since her first pregnancy.

"Every night [...] since I was pregnant, hands down, even if things aren't going great and he's still snoring, somehow he knows how to massage my back," she revealed earlier this year.