This is Macy’s idea of a Millennial Wonderland

SELFIE WALLS! Wearables! 3-D printers! The newly renovated basement at Macy’s massive flagship store in New York City’s Herald Square is full of millennial buzzwords. It’s called One Below, and the department store wants it to be a destination for young shoppers.

One Below is part of a $400-million renovation at Macy’s flagship location and is an interesting experiment. Instead of being segmented by types of merchandise, such as the store’s shoe floor or home goods section, the new area mixes all kinds of products for the 13- to 22-years old.

It’s essentially its own 53,000-square-foot store filled with technology, apparel, accessories, cosmetics, food, and a constant electro soundtrack of house music. It’s larger than every Macy’s Backstage outlet store in the country.

Macy’s has never had an issue attracting shoppers ages 30 and above, but since 2012, it has been actively trying to lure younger people into its 800 or so locations.

One Below will be a test to see what resonates with young people, said Macy’s chief merchandising officer, Tim Baxter. While it’s logistically impossible to roll out such big spaces for millennials nationally, Macy’s plans to take pieces from One Below and use them in its many mall stores.

Fashion labels such as Material Girl, Roxy, and XOXO are found in the apparel area, which is anchored by a large display of clothes from American Rag, an exclusive label. In one corner sits the dress department, outfitted with sparkly items for prom and homecoming.

There’s plenty of fancy new tech, and customization is a theme throughout the floor. The Levi’s jean shop allows customers to personalize their denim with embroidered designs, using a laser-etching machine (“tattoos for your jeans,” as one employee put it). Samsung Electronics gadgets, such as the Gear Fit watch, are featured in the wearables area near Fitbit fitness trackers.

A 3-D printing shop offers up jewelry and iPhone cases that can be created with 3-D Systems’ Cube device. A Fossil desk lets shoppers build their own watch and add an engraving.

Soon, Macy’s will be adding a photo booth for shoppers to get their picture taken, then get it printed into a figurine — a 3-D selfie.

In cosmetics, there’s a MAC makeup shop alongside a Benefit BrowBar. If you want Estée Lauder or Lancôme, you’ve come to the wrong place. A hair-dry bar will open shortly.

In accessories is a particular collection of Calvin Klein bags, cheaper and more colorful than most of the label’s higher-end items. There are also accessories from Betsey Johnson and Vera Bradley, which Macy’s says are popular with millennials.

With its pumping music and bright decor and graphics, the whole floor feels like a club compared with the levels of adult goods above. Selfies are encouraged. A video wall shows Instagram photos from people who have tagged the store, and there’s a “selfie wall” to take photos in front of images of New York City landmarks — including the exterior of the store they’re in. “This is the selfie generation,” said Mr. Baxter.

Along with the changes at the flagship, Macy’s has expanded its Backstage stores and its recently acquired Bluemercury beauty shops with the hope of getting millennials on board.

Oliver Chen, an analyst at Cowen & Co., wrote in a note to clients that although the moves don’t add a lot of sales, they’re encouraging signs, especially for the “antiquated” beauty department.

“We like the focus to diversify the business, expand the service offering, and perhaps most importantly increase brand awareness with millennials,” wrote Mr. Chen. — Bloomberg