When Stranger Things premiered in 2016, its heroes were mere children, up against the impossible task of fighting interdimensional evil. As the sci-fi series approaches its fourth season, debuting May 27, its stars have all grown up. A lot. The core group of characters is now in high school, figuring out where they fit in the social hierarchy, all while juggling relationships and heartbreak. 

With so much change over four seasons, you’ll probably be wondering just how old the kids of Stranger Things are in real life. We’ve got the answers, explaining everyone’s ages when their introductory season premiered — and now. This is way easier to understand than the Upside Down. 

Millie Bobby Brown, Eleven

Left: Curtis Baker/Netflix

How old they were then: 12  How old they are now: 18 

Most 18-year-olds are proud of themselves if they’ve learned how to drive by the time they finish high school. Millie Bobby Brown, on the other hand, has been far, far busier. Since bursting onto the scene as Eleven in Stranger Things Season 1, she has led an entire other Netflix franchise (the YA British mystery series Enola Holmes), starred in two Godzilla blockbusters and launched her own makeup line, Florence by Mills. She now has three more Netflix movies in the works: fairytale twist Damsel, thriller The Girls I've Been and children’s book adaptation The Thing About Jellyfish. 

Finn Wolfhard (Mike Wheeler)

Left: Curtis Baker/Netflix

How old they were then: 13  How old they are now: 19 

Before Stranger Things debuted, Finn Wolfhard was a tween with a few minor roles in genre series like Supernatural and The 100. Since the world met Wolfhard as Mike Wheeler, he’s gotten a major horror franchise under his belt with It and struck out on his own creatively. Wolfhard is the frontman for his band Calpurnia and served as a co-writer and co-director of Spendtime Palace’s 2017 music video “Sonora.” 

Noah Schnapp (Will Byers)

How old they were then: 11 How old they are now: 17 

Noah Schnapp is the youngest member of the original Stranger Things crew at just 17. Despite his age, Schnapp, who plays Will Byers, still boasts just as lengthy a resume as his co-stars. Schnapp appeared in the Halloween comedy Hubie Halloween and Sundance selection Abe. His next project is mystery-thriller The Tutor. 

Caleb McLaughlin (Lucas Sinclair) 

How old they were then: 14  How old they are now: 20 

While Noah Schnapp is the youngest OG Stranger kid, Caleb McLaughlin is the oldest at 20. Before making his mark as the resident Stranger Things pragmatist Lucas Sinclair, McLaughlin made his Broadway debut as Young Simba in The Lion King. Since then, he has starred in sports drama High Flying Bird and Concrete Cowboy, alongside Idris Elba. You can see him next on Netflix in the Lee Daniels horror movie Demon House. 

Gaten Matarazzo (Dustin Henderson)

Left: Curtis Baker/Netflix

How old they were then: 13  How old they are now: 19 

Like McLaughlin, Gaten Matarazzo came to Stranger Things as a Broadway veteran, starring in both Priscilla, Queen of the Desert and Les Misérables as a tween. The 19-year-old has stayed busy since introducing viewers to Dustin Henderson with his own prank show, Prank Encounters, and a guest appearance in kids show Waffles + Mochi. He’s now teaming up with fellow Netflix actor Angourie Rice, of Senior Year, for high school comedy Honor Society. 

Sadie Sink (Max Mayfield) 

How old they were then: 15  How old they are now: 20 

Sadie Sink may have joined Stranger Things in Season 2 as skateboarding cool girl Max, but she fits right in with the rest of the cast at 20. Following her breakout part, she had a starring role in the Fear Street spooky saga and shattered the internet as the heroine of Taylor Swift’s “All Too Well” music video. Sink’s star continues to rise as she appears in two upcoming movies, drama Dear Zoe and Darren Aronofsky’s The Whale. 

Priah Ferguson (Erica Sinclair) 

How old they were then: 11  How old they are now: 15 

Like the class of Stranger Things kids ahead of her, Priah Ferguson joined the show as just a tween, at age 11. She’s now 15, and you can catch her stealing scenes in Stranger Things or in the upcoming horror comedy Boo! 

Anniston and Tinsley Price (Holly Wheeler)

Left: Curtis Baker/Netflix

How old they were then: 3  How old they are now: 9 

When you see Holly Wheeler in Stranger Things Season 4, you just might be surprised how independent Mike’s formerly toddling little sister has become. That’s because the actors portraying Holly, twins Anniston and Tinsley Price, turn 10 this summer.