20 years later, we're still waiting for our letters from Hogwarts.

Harry Potter and the Philosopher's Stone arrived in book stores 20 years ago today, on June 26, 1997. Over 500 million copies, 8 films, a play, a spinoff series, a website, and three theme parks later, Pottermania is still going strong, as Harry Potter remains the bestselling children's series of all time and a huge part of popular culture.

The series began on a train ride from London, when the idea of a boy traveling by train to a wizarding school popped into author J.K. Rowling's head. Through her mother's death, depression, divorce, poverty, and single-parenthood, Rowling wrote; and from her imagination came a world full of adventure, magic, and heart - a world that children of all ages would delight to visit time and time again for years to come.

Today, Rowling expressed her gratitude to her fans on Twitter for the chance to share that world with them.

20 years ago today a world that I had lived in alone was suddenly open to others. It's been wonderful. Thank you.#HarryPotter20

— J.K. Rowling (@jk_rowling) June 26, 2017

Fans have responded by thanking her in turn:

Thank you for making our imagination a far better place to live.

— Michael Faudet (@MichaelFaudet) June 26, 2017

No, thank you. You gave my kids the love of reading. And had me bloody hooked too.

— Paul Syvret (@PSyvret) June 26, 2017

Thank you @jk_rowling for creating a ?where girls can be smart, brave and save the boys from failing ❤#harrypotter20  #Hermione @wwbookclub

— Allie (@mugglemayhem0) June 26, 2017

Thank *you*. I went through a lot of painful stuff as a young adult and hanging out in the world you created made it a little bit better. ?‘?

— EricaJoy (@EricaJoy) June 26, 2017

#HarryPotter20 is surreal to see. My entire childhood revolved around this series. Seriously felt like I grew up with the kids at Hogwarts

— abdul ? (@Advil) June 26, 2017

Thank you. You've put a lot of a magic into peoples lives. ✨

— Cherry Wallis (@CherryWallis) June 26, 2017