Four years ago, Edina sisters Isabel and Caroline Bercaw needed a summer project.

They had started making their own bath bombs because they didn’t like what was in the stores. A friend suggested they sell them at the Uptown Art Fair in Minneapolis that August.

So the sisters, then 11 and 12, got to work making 150 of them. To their surprise, they sold out the first day and had to scramble to make more that night to sell on day two of the fair. They sold out that day, too.

“It was really exciting for us, because we didn’t really think anything of it, and its potential,” said Caroline, now 15.

The next year at the fair, a local salon owner approached them wanting to sell the bath bombs at his business. The Bercaw family thought the teens might be onto something.

Next came a website and Instagram account for Da Bomb Bath Fizzers in April 2015, and the business slowly grew organically to the point that the family had eight people helping them make and deliver the bath bombs.

Then their lives changed. Target approached them in January 2016, and the family had a decision to make — and went for it. Mom Kim had a background in marketing. Dad Ben was a business consultant. They decided to make it a family business with Kim as CEO and Ben as chief financial and operating officer, with the teens continuing to be the driving force behind it.

“We knew that we had to jump all in 150 percent,” Caroline said. “This was the turning point. This was going to be something bigger.”

Edina High School worked with the family so the teens could both run their business and finish school.

In April 2016, they opened a warehouse and manufacturing facility near Interstate 494 in Edina to fulfill growing orders.

A year and a half later, the teens have trademarked the term “sisterpreneurs,” they have expanded into 45,000 square feet of space, employ 150 people and their products are in more than 7,000 stores in all 50 states and Bermuda. Revenue is expected to increase more than 500 percent this year and top $10 million.

Isabel Bercaw, now 16, said while they continue to develop new scents and themes for the bath bombs, the basics have stayed the same.

The girls experimented, using recipes in books and online and watching YouTube videos to find the right mix of ingredients for their bath products.

Even when they were making the bath bombs for themselves and friends, they had decided to use high-quality ingredients like commercial grade moisturizers so the bath bombs wouldn’t stain tubs or leave residue on people’s skin.

They also thought it was fun to have a surprise in the middle, similar to the prizes in cereal boxes and a feature that made their products stand out to retailers like Target, Ulta Beauty and Hot Topic.

The sisters had a natural eye for marketing. Most products they saw in stores had pastel or white packaging, so they made their packaging black. They have developed it further in the four years, with help from marketing professionals, and now have a patent pending on their packaging.

The next step was making the products fun. There’s the Galaxy Bomb, which makes the water black. There’s the Cake Bomb, with sprinkles on it. Each has a scent matching the theme.

The latest products have brought brother Harry, 11, into the business. He let the family know that young boys were using the products, too, opening a potential untapped customer category, Isabel said.

So Harry helped Isabel and Caroline design the Ninja, Bug and Sporty bombs.

“It keeps people coming back. It ensures there’s a bath product for everyone,” Isabel said.

The Earth Bomb is “really important” to the sisters, Isabel said. Partial proceeds go to charities that protect the world’s oceans, and the company Instagram account also promotes that cause.

“One of the things that is important is that when people are less fortunate than yourselves … and you’re an influencer, using your power for good,” Isabel said.

The sister’s journey is far from over, they say.

More products are in the works.

They have a book set to publish in August, Caroline said.

“And we really want to expand into the international markets” beyond Bermuda, Isabel said.

That might be a lofty goal, but the sisters said their “fearlessness,” “cluelessness” and “obliviousness” to business norms and challenges actually helped them go for opportunities others might be hesitant about.

For example, they didn’t know that an “end cap,” which is a product display at the end of a store aisle, was as coveted and competitive as it was.

“We jumped right in, and I think it really helped us,” Isabel said.