For the better part of the last four years, Julie Averbach has been visiting as many Trader Joe's supermarkets as possible. 

She's been to more than 150 locations in 20 states while researching her upcoming book, "The Art of Trader Joe's", in which the Yale art history grad breaks down the chain's branding and iconography. 

"If I was ever going to visit a friend in an area that I hadn't been to, I'd make sure to go to the local Trader Joe's," she says. "There were certain road trips where I would go to the Boston area or DC and visit 10 Trader Joe's stores in one day, just driving straight from one to the next." 

While the task of visiting hundreds of supermarkets may sound tedious, Averbach says it has been anything but. 

"Each Trader Joe's is very much unique," she says. "The artwork is very personalized to reflect the local community. They all tap into a sense of local pride and identity, which is something that I think is really unique for a grocery retailer."

During her hundreds of hours spent in Trader Joe's stores, Averbach has observed the things the retailer does that have made it such a fan favorite. She sat down with CNBC Make It to talk about three things that have helped Trader Joe's build its loyal following.

Embracing private label products

More than 80% of the products Trader Joe's sells are private label, according to the supermarket's official podcast. And while non-brand-name products at most supermarkets are often shunted to the side in favor of their name-brand counterparts, at Trader Joe's their products are front and center in unique, eye-catching packaging. 

"There's this kind of stigma that private label is something that you settle for so that you can pay a lower price than you would for the name brand option," Averbach says. "At Trader Joe's, the private label products are affordable luxuries." 

"The packaging and the art and design play an important role in turning these private label products — something that would be perceived as perhaps less expensive and inferior in quality — into something that feels high quality and attractive for a customer," she continues. 

Indeed, products like Trader Joe's Dark Chocolate Peanut Butter Cups, Peanut Butter Filled Pretzel Nuggets and Unexpected Cheddar are among the chain's best-selling items. 

Trader Joe's turns shopping into an experience

While every Trader Joe's is unique, Averbach says they all have certain things in common when it comes to their designs.

"When you walk in the store, the first thing is you smell fresh flowers near the entrance," she says. "You hear upbeat music on the speakers. You're going to look around and see eye-catching products on the shelves, vibrant, colorful artwork and signs throughout the store. Many stores also have sampling counters for tasting products." 

These decisions help it not only sell groceries, but also to "create the most joyful experience possible for the customer."

By turning each store into an eclectic, interesting place to browse, Trader Joe's encourages shoppers to look around and find something they might like.

"Trader Joe's is encouraging us to slow down and actually enjoy the shopping experience," Averbach says. "And once you slow down and enjoy, you're also more likely to discover and buy things that weren't on your original shopping list." 

Encouraging exploration with exciting packaging

Trader Joe's knows how to get customers excited about its products.

A box of chocolate cookies isn't just a box of chocolate cookies at Trader Joe's. Instead, it's marketed as "Astounding Multi-Flavor Joe Joe's" and packaged in a unique hexagonal box designed to make the cookies look like they're headlining a circus act.

These choices make you more likely to want to try a product, or even give it to someone else.

"Trader Joe's is really expert at packaging products to make them feel like novelty items and very giftable items as well," she says. 

When it comes to flavors that might be foreign to its customers, Trader Joe's doesn't stick them in the international aisle. Instead, the store highlights its products as things you should try.

In her book, she writes about how the chain's "worldly product packaging" satisfies a desire to travel without having to leave home.

"At Trader Joe's, the entire store is like an international aisle," she says. "Shoppers are more likely to explore and discover products that they didn't original plan on buying."

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