He was 26-years old and leisurely strolling through a flea market when Gene Smith's eyes landed on something familiar.

A piece of his childhood. Nostalgia in cherry red.

"It was about 1997, I went to a flea market and was looking around," he recalled. "I had them as a kid but seeing them again there—I was hooked."

Fast forward a couple decades and Smith's collection has grown to "at least a couple thousand" cars.

Though he's sold a few, Smith said he mainly buys for fun.

Hot Wheels have changed a few times over their 50 year history—and Smith's collection has changed, too.

"Everyone collects what they like best. For me, it's muscle cars, particularly ones from the 60s," he said."Somewhere over the years I switched and started collecting Mustangs and Camaros…For me it's all about the muscle cars."

As far as collecting goes, Smith said it doesn't get much better than Hot Wheels.

They're inexpensive, accessible and there's something for everyone, he says.

"And who doesn't like cars? You wish you could have the real thing, but you'll settle for a Hot Wheels," he laughed. "There's old guys that collect, and young guys that collect—it's for everyone."

He said he's met other collectors along the way.

"One time I was searching through a Hot Wheels display and met a guy. I happened to be in Mustangs and so did he. He said 'man I need to get rid of my collection," So we exchanged numbers and later met up and I bought his collection of Mustangs," Smith recalled.

A sea of Hot Wheels, both on display and in packages, fill Smith's residence

Despite the overwhelming number, Smith said, "There's one."

One that stands out from the rest, one he says may be his favorite.

"I have a Cobra that Carol Shelby signed, so that's probably my favorite," he said. "I bought it on bay when I was in Afghanistan in about 2003. It was about 2009 when I met him at an event in Tulsa and had him sign it. I love it."

Collecting comes easy to Smith, but he has some tips for those just getting started.

"Collect what you like. Don't go chasing after stuff just for the sake of having it, if you don't love it," he said. "And display things. Why have it if you're not going to see them? Where's the fun in that?"

Since Hot Wheels, an invention of Elliot Handler, husband of Barbie doll inventor Ruth Handler, Mattel has sold more than four billion of the miniature vehicles.

While some remain in pristine condition, on the shelves of collectors like Smith, others show the wear and tear of generations of play.

"That's why they've lasted so long, I think," Smith said. "They're for everyone. They're a piece of our childhood but they're more than that. There's always something new."