Mars is investing in Kind, giving the M&Ms-owner a stake in the bar brand made of ingredients "people can see and pronounce."

Kind, founded in 2004, was one of the first popular snacks to eschew artificial flavors and preservatives. With Mars' investment, the Snickers-owner gains an entrance into this increasingly popular trend and Kind the resources to expand upon it.

"Our vision is that Kind is going to become the foremost health and wellness platform," said Daniel Lubetzky, founder and CEO of Kind.

The deal gives Mars the option — though not the requirement — to fully acquire Kind down the road, according to a source familiar with the situation. It values Kind at roughly $3 billion, though potentially as much as $4 billion, depending on how quickly Kind grows.

The now $33 billion U.S. snack category has ballooned along with hectic Americans' schedules that force them to eat on-the-go. Busy households today spend on average $133 annually on individual snack items, according to research firm Nielsen. The fastest growing snack items are those with a health focus, like organic or free of artificial flavors.

That growth has attracted investment from larger food companies. Earlier this year, Conagra acquired Boomchickapop popcorn's parent company Angie's Artisan Treats, and Kellogg acquired RXBar for $600 million.

The boom has also invited new competitors. Lubetzky said the industry lost about 15 percent of its market share to copycat playersin 2015 and 2016. Many of those brands though have struggled to maintain sufficient sales to ensure placement in retailers, he said.

In Europe, the snacking category is far more nascent. European diners still tend to enjoy sit-down meals.

Kind sells through distributors in 14 countries, including Mexico, the United Kingdom and Ireland. With Mars' investment, Kind expects to double down in those countries while expanding in others.

Going to those countries now, ahead of the potential rising trend, prevents Kind from appearing like a "me too" player, said Lubetzky.

"If somebody borrows our playbook and goes there first, we might be perceived by consumers as a copycat... We want to go there faster."

With Mars' investment, Kind also expects to build out its products, both through innovation and acquisition. Kind already makes breakfast bars, clusters and fruit bites. Categories the company could move into — though no decisions have been made — include beverages and frozen food.

Private equity firm VMG group bought a stake in Kind in 2008. It later sold back its shares to Lubetzky in 2014 in a stake sale that valued the company at $728.5 million.