Mindy Russell was a little surprised when Cooper, her 5-year-old son, asked for a GoPro for Christmas.

GoPro video cameras tend to sell for hundreds of dollars and are often used by people who want to record themselves participating in outdoor activities, less by young boys at an age typically associated with first learning to ride a bike.

It’s not the first grown-up gadget he’s asked for. Cooper, like many children, is a fan of unboxing videos on YouTube, a genre that originated on the video platform and has grown into its own cottage industry where people open up anything from toys to expensive electronics.

“He asked for a drone first, and I said that’s a big no,” Russell said.

Unboxing videos have been on YouTube for years, and their popularity has only continued to grow with time. They’re appealing to almost every demographic on the site, but they have a particular draw for children.

The videos are particularly popular around the holidays, according to YouTube search data from Google Trends. With the holiday season in full swing, many of these videos have informed the Christmas wish lists of children across the country, and for some who can’t afford lavished items, it allows their children to live vicariously through an unboxer.

But experts warned that unboxing can be seen as unmitigated and relentless advertising to children, who often don’t know the toys or electronics are given to a YouTuber with a large following as part of new-age marketing.

Google Trends show that the interest in the term "Unboxing" has increased over time. Google

“I think that’s one of the things parents are really in the dark about, because we expect programming to be regulated, knowing that our kids are highly impacted by commercial marketing,” Caroline Knorr, senior parenting editor at Common Sense Media, said. “Those regulations are not in place in non-traditional broadcasting.”

Jori Mattocks’ daughter, Jordyn, 9, is partial to unboxing videos of Shopkins, tiny collectable toys in the shape of food like “Wendy Wedding Cake” and “Carrie Carrot Cake.” But Jordyn also sees people unboxing more expensive items, such a Barbie DreamHouse — something Mattocks can’t afford.

“You have to break the news to the kid that it’s not something you can do,” Mattocks said. “For them, perception is reality, and they think everything online is real and you have to remind that’s not the case.”

Mattocks said she saw some upside in the videos.

“A lot of these toys are so expensive and I can’t get them for her,” Mattocks said. “These videos allow her to see all things we can’t afford to buy or get our hands on.”

Box $ocial

Making unboxing videos can be a lucrative business. CKN Toys, a children’s channel on YouTube that often posts unboxing videos, has more than 10.2 million subscribers. A video posted to the channel unboxing a “Spiderman 6-Volt Battery-Operated Ride-on Car” has more than 268 million views.

Mothers and experts who spoke with NBC News about the phenomenon of unboxing videos mentioned one standout channel that many children gravitate toward: “Ryan ToysReview.”

The family-friendly channel features Ryan, 7, unboxing popular toys, many of which he says he donates after filming. The channel has amassed more than 26 billion views, and Forbes estimated the channel made $22 million in a 12-month period.

Part of why the YouTube videos have such a popularity among children, according to Knorr, is the format, which can’t be found elsewhere.

“A large part of the appeal is the novelty. It’s a format you don’t see anywhere else,” Knorr said. “YouTube is sort of a genre unto themselves, and there’s no other place to go for those kind of videos.”

She also said the format allows children to feel a personal connection with the person they’re watching unbox an item.

“I think kids develop emotional attachment, like it’s a friend who has the product,” Knorr said.

And like Mattocks’ daughter Jordyn, the element of surprise makes the videos exciting for children and holds their attention.

“When you’re talking about unboxing, I think it’s beyond living vicariously,” said Adam Pletter, a child psychologist. “I think biologically they’re driven by the excitement of what they’re about to see.”

A lack of transparency

One of the biggest issues experts have with unboxing videos is the lack of transparency that exists in the genre.

“Kids don’t know that the hosts are getting the product as a way of advertising the product,” Knorr said. “[Ryan ToysReview] is basically doing ads for a company.”

YouTube has policies around paid placements and endorsements that require creators to notify viewers if they receive compensation for featuring a particular product. YouTube declined to comment.

Knorr warned that some children who are overexposed to commercialized productions can chip away at a child’s self-esteem.

“Overexposure to highly commercial content … can make people feel a sense of not feeling secure,” Knorr said. “Research shows that always wanting a new thing doesn’t satisfy that craving, and you feel a little bit crappy.”

Mattocks said she feels the pressure of not being able to afford the more expensive items Jordyn wants, but has used the unboxing videos to teach Jordyn about the benefits of hard work.

“It helps her to understand just because you see something on TV or in a video doesn’t mean you can have it,” she said. “You can make list of goals and work to achieve them.”

Russell said her son has been understanding of her boundaries on what he can and can’t have, and experts say parents are the ones who need to set the guidelines for how their children interpret unboxing videos.

And Russell said as long as Cooper is watching kid-friendly channels like Ryan ToysReview, she takes no issue with him watching unboxing videos.

“A lot of people have a negative opinions of kids watching these videos, but I think it’s harmless as long as stay on right channels,” she said. “I don’t see a problem with it.”

CORRECTION (Dec. 23, 2018, 12:07 p.m. ET): An earlier version of this article misstated Ryan’s age. He is 7, not 8.