The cast of “Young Sheldon” is shocked by the news of the sudden death of a member of the film crew hue01

Iain Armitage is celebrating his 18th birthday.

The actor — who first got his big break when he appeared in season 1 of Big Little Lies — became part of a television legacy when he landed the role of Sheldon Cooper in Young Sheldon, the prequel series of The Big Bang Theory. The show, which started filming when Armitage was just 8 years old, ran for seven seasons from September 2017 to May 2024.

Before the series finale aired, Armitage looked back on growing up while filming Young Sheldon, noting that his younger self would have been “so surprised and happy to see where we are now.”

“I don’t think this kid could have anticipated what it would feel like to film our final scene all these years later,” Armitage wrote on Instagram in April 2024. “Thank you, amazing crew, past and present, and those who have been there the whole time. I love you all so much!”

On July 15, Armitage turned 18 years old, a milestone he reflected on via a July 2026 Instagram post. “Can’t believe I’m gonna be 18 in two days- thank y’all for all the love✌️,” he wrote.

Below, see 11 sweet photos of Iain Armitage on the Young Sheldon set over the years.

Polished in the Pilot

Iain Armitage on Young Sheldon. — Iain Armitage on ‘Young Sheldon’ in 2017.Robert Voets/CBS via Getty

Young Sheldon premiered on Sept. 25, 2017. In the pilot, seen here, Armitage plays 9-year-old genius Sheldon, who shows up to high school donning a bowtie and equipped with a briefcase.

Hard at Work

Armitage was all smiles on set, including during season 1, episode 12, which aired in January 2018. The episode followed Sheldon as he asked for a computer.

Tap Dance

While Armitage nailed his portrayal of an analytical, smart kid, he performed a compelling tap dance number in season 1, episode 16, which aired in March 2018.

Suited Up

Armitage often looked sharp in his Young Sheldon costumes. This suit ensemble, featured in season 1, episode 18, gave the young actor a distinguished look.

Sibling Time

Iain Armitage, Raegan Revord and Montana Jordan on the set of Young Sheldon. — Iain Armitage, Raegan Revord and Montana Jordan on the set of ‘Young Sheldon’.Young Sheldon CBS/Instagram

Armitage hung out with his on-screen siblings, Raegan Revord and Montana Jordan (who played Missy and Georgie, respectively), on set. On this day in 2018, they had special visitors: a pair of cows.

Family Fun

Iain Armitage, Lance Barber and Raegan Revord on the set of Young Sheldon. — Iain Armitage, Lance Barber and Raegan Revord on the set of ‘Young Sheldon’.Young Sheldon CBS/Instagram

While filming, Armitage also spent time with the rest of his on-screen family, including actor Lance Barber, who played his dad, George Cooper Sr. Here, Armitage, Revord and Barber can be seen here striking a fun pose.

Big Joke

Iain Armitage on the set of Young Sheldon. — Iain Armitage behind the scenes of ‘Young Sheldon’.Young Sheldon CBS/Instagram

Armitage showcased his sense of humor in this 2020 behind-the-scenes photo of himself “stuck” in a toilet, with his perfectly combed Sheldon-style hair intact.

Angry Face

Naturally, Armitage tapped into Sheldon’s many emotions. Sometimes, that meant channeling an angry face, as seen in this photo from season 5, episode 14, which aired in February 2022

Style Reinvention

When Armitage’s Sheldon began going through puberty, he tried out this new style. Featured in the season 5 finale, the look gave him an edgier vibe than his typical polished appearance.

Costume Reality

Costumes aren’t always comfortable. Armitage wrote on Instagram in May 2024 that the hazmat suit he wore during season 7 “got a little stifling, so going outside for fresh air felt good.”

All Grown Up

Armitage rocked Sheldon’s signature plaid shirts and side-swept hairstyle, seen here in season 7, throughout the entire series.