MINNETRISTA, Minn. – From Legos to baseball cards, the kid has never been created who doesn’t crave a collection.

But Maria and Miller Williams are the only children on their block whose collection includes an alligator skull, a reindeer pelt and a Black Angus cow pelvis.

“They both have been just into nature,” says Anna Williams, mother of 9-year-old Miller and 10-year-old Maria.

For years, Anna and her husband Nick Williams have been watching their children’s blossoming interest in nature - never sure what Maria, in particular, would come carrying home in her hands.

Maria and Miller Williams have been fascinated with nature, almost from the time they could walk.

“I can remember there was a spider the size of her palm,” Nick laughs, still feeling squeamish at the thought of it.

But then spiders begot beaver skulls, peacock feathers and turkey beards.

And then Maria had a revelation: “I really like museums a lot and I thought, ‘Why not have my own museum?’”

And now Maria and her brother have just that, albeit at the expense of Miller’s bedroom.

The “Tiny Natural History Museum” opened last year in the space where Miller used to sleep. He’s now taken the top bunk in his sister’s bedroom.

Miller Williams holds up a sign for the museum he started with his sister

“That's cool, that’s fine with me,” he assures a visitor. Maybe it is. Or maybe he’s just learned it’s better not to resist.

“She doesn't back down easily,” Miller says of his sister.

Maria stands nearby with a piece of coprolite. “It’s also called dinosaur poop,” she explains - the blob of the turd fossil in her palm.

Maria’s parents have experienced her persistence too, as they attempted to gently persuade her from opening her in-home museum to the public.

“We would say, ‘Well, I don't think the homeowners association, you can have a museum in your house,’” recalls Anna.

Maria read the bylaws.

“There's no rule against it,” she proudly proclaims.

Nick recalls another of his favorite Maria stories. “I remember coming home one time and asking her, ‘If I give you ten bucks, can I be a lifetime member?’ And she said, ‘Well, no, that's the silver plan.’”

Maria set daily admission at $2, then added a gift shop to increase revenue, featuring handmade cards and jewelry.

She also started setting her sites on something larger. “We had grandmas and grandpas and family that would come through the museum and pay money,” says her mom, “but it just wasn't big enough.”

Then, last month, Maria and Miller took their museum on the road to the Southshore Community Center in Excelsior.

Maria pondered bathroom advertising, before going with social media and flyers passed out to her hockey team.

“We were shocked,” her mom admits. “We had 75 people come.”

Miller and one of his friends worked the admission table, while Maria served as the docent.

George Wieblen of the Bell Museum of Natural History gives Maria and Miller Williams a private tour.

Over the course of three hours, they earned $250 – half of which they donated to a less tiny museum, the Bell Museum of Natural History at the University of Minnesota.

Beverly Anglum, the Bell’s advancement director, accepted the donation – mostly small bills and coins – in a bulging Ziploc bag.

The Bell Museum presented Maria and Miller with a few small artifacts for their own collection and offered them a behind-the-scenes tour of the museum’s research wing.

Anglum marvels at both the donation and the way Maria and Miller raised the money.

“What they’re doing can really connect others with really generating this love of nature,” she says.

A few feet away, Maria and Miller stroke a live snake, being held by a Bell Museum curator.

“They smell with their tongue,” Maria explains to Miller, his own eyes glued on the slithering reptile. “Whoa, that is so cool,” he whispers.

Their parents watch from 15 feet away.

“This is a good distance,” says Nick.

“That's not happening in our house,” adds Anna.

At the same time, they know better than to count their daughter out.

“What’s next?” asks Nick rhetorically.

“Who knows?” he answers.

He pauses to reflect.

“Who knows?”

Note: Maria and Miller Williams have been invited to display part of their collection at the Bell Museum of Natural History on March 26th. The siblings will be present during the Saturdays with a Scientist program running from 11 a.m until 2 p.m.