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It’s hard to remember a world before Harry Potter. The children’s book series is a juggernaut that spawned a film series, theme parks, a Broadway play and museum exhibits. It’s been 20 years since readers in the U.S. were first introduced to the wizarding world, and more than 500 million copies of the books have been sold worldwide.

The series is still intensely personal for the boys and girls who have read, and still read the books. It’s also had a deep impact on what children read.

At the New York Historical Society, a new exhibit called “Harry Potter: A History of Magic” traces the roots of author J.K. Rowling’s novels — and it’s filled with Potterheads of all ages. Inside the museum, curator Roberta Olson is justifiably proud to show what she’s got.

“We have all kinds of basilisks here,” Olson says. “Unbelievable objects. The sphinx, you can touch.”

There are books flying overhead, tinkling music coming from a crystal ball, the shadows of unicorns and hippogriffs. There are also centuries-old objects that J.K. Rowling used for inspiration.

That includes Bezoars, or rather, “stones” formed in the stomachs of goats, thought to be antidotes to poison — they’re real. So are mandrakes, though it’s unclear if they actually scream.

Inside The Ever-Expanding Wizarding World: Harry Potter At 20