“You are officially tall enough to ride without a booster seat,” our pediatrician tells my daughter after reviewing her measurements. It was her 9-year check-up, and she’d grown three inches in a year, landing at the 96th percentile for her age. She’d likely been tall enough for months, but I insisted we wait for her doctor’s confirmation, comforted by the imminent discussion on sitting safely sans booster.

My girl gleefully melts into the car’s fabric and buckles her seatbelt, flashing a smile that showcases an assortment of adult and baby teeth. Reality hits me like an airbag in the face: she’ll never need a car seat again. I run my fingers over the faint indentation where the infant seat once rested, remembering how it became heavier as she plumped into a toddler. I once carried her around by a handle, and now I can’t lift her at all.

In many ways, she’s still a little girl.

She talks to her stuffed animals, apologizing when she steps on their feet. She won’t even consider going to bed without her favorite stuffed dog, Bella. Her forceful footfalls shake the floor as she frantically races to our bedroom after a nightmare.

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But moments that foreshadow her tween years are starting to peek through. She carefully picks out her clothes for school, looking in the mirror as she places a matching headband onto her head just so. Written notes and homemade bracelets have replaced the pictures of flowers and hearts she once drew for friends. Television shows that she used to love, are now “for babies.”

Nine is her first step on the trail to tweendom as she yearns to be more grown-up but is afraid of it simultaneously.

Harry Potter movies draw her in, but Voldemort scares her. She’s excited to go down the steepest slide at the waterpark but hesitates at the top. She wants to play laser tag at the birthday party but asks me to come because it’s so dark.

The words “Big Kid” in bold print on her clothes jolt me as I fold laundry. Her top two permanent teeth dominate her little face when she smiles. She sits on my lap, her weight crushing my chest, but I readjust my body to hold her close because I know, sometime soon, she may no longer even try.

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I look at the empty passenger seat beside me where she’ll sit in a few short years, and it reminds me there are so many milestones yet to come. I take a deep breath, collect myself, and drive forward with my big kid because the truth is, I’m the passenger. The journey is hers.