Remember the glass blocks of ‘80s bathrooms? They’re back.

Along with 1980s neon manicures and vintage ‘90s blazers, glass blocks are making a comeback thanks in part to a new fan base on social media. One Instagram reel showcasing several types of the retro building material has racked up more than 5 million views since March. It features cross-hatched blocks, frosted blocks and fluted blocks, underscoring the fact that the latest iterations aren’t always quite what you remember from your aunt’s gaudy apartment or the restaurant with a smoking section where you celebrated family birthdays.

Glass blocks have more than just good looks going for them, too. They’re a relatively affordable choice for homeowners who want to add architectural interest or natural light without sacrificing privacy. They’re even known for enhancing fire safety.

“Glass blocks have this inherent luminosity to them, while also solving … technical problems,” says Brendan Guerin, founding member of the firm Guerin Glass Architects, which operates in Honolulu, Los Angeles and Brooklyn.

Here’s why the glass block renaissance just makes sense.

There’s a very good reason glass blocks became so associated with luxury ‘80s and ‘90s bathrooms: They let in natural light without exposing inhabitants to the outside world the way a typical window would. This remains a key draw for architects today.

Brad Swartz of Brad Swartz Architects, a firm that specializes in urban spaces in Sydney, explains that glass blocks were an ideal solution when he was tasked with designing a home in an alleyway, along with designer Henry Wilson. The location was dark and tight, with neighbors in close proximity. Swartz stacked glass blocks, etched on one side to enhance privacy, around nearly the entire front of the house.

“The way they let light through is really beautiful and changes throughout the day,” he says. This project drew inspiration from one of the most enduring glass block masterpieces: the Maison de Verre, a 1930s residence in Paris distinguished by its glass blocks with circles in the center. Like Swartz and Wilson’s alleyway project, the Maison de Verre includes entire walls of the material.

Brent Buck, principal of Brent Buck Architects in New York City, says it’s that variation that separates the contemporary glass blocks from the 1980s and ‘90s ones. “I think when people think of glass blocks, they go, ‘Oh, there was one specific type of glass block’ and it was ubiquitous for that time period.”

Christopher Adams, founder of Pohio Adams Architects, also in Sydney, turned to glass blocks for a past project in a challenging location. The home backed up onto an apartment building, giving many of those neighbors a direct sightline into the property. To shield his clients from prying eyes, Adams encased the first floor with glass blocks. The result? “This lovely, watery light, and you were unaware of the suburban surrounds.”

Both Adams and Buck say some of their recent glass block projects took cues from New York City’s Soho neighborhood, where you’ll find small, circular glass bulbs inlaid on Broadway and Canal streets. They’re easily mistaken for art, but they’re actually remnants of Soho’s past as an industrial center. According to the Soho Broadway Initiative, they were known as vault lights or deadlights, and functioned as tiny skylights that illuminated factory basements. To provide natural light for his client’s basement and some architectural interest to a kitchen, Adams similarly “set cast glass pavers into the concrete slab under the timber floor of the kitchen.” Along with the filtered light, says Adams, “it creates this beautiful shadow effect when someone walks over it.”

While cost for individual projects is highly variable, the architects interviewed for this story described glass blocks as an affordable option. Guerin even crunched the numbers for us, estimating that a glass block wall, including labor and installation, would typically cost $30 to $40 per square foot. By comparison, he says, a traditional glass wall could run closer to $100 per square foot.

“The glass blocks have an air pocket in the middle of them,” explains Swartz. “They’re not solid glass, and that affects the price.” But keep in mind that glass blocks are not the same thing as glass bricks, which are generally rectangular, rather than square, and solid glass without an air pocket. This makes them almost prohibitively expensive for most renovators’ budgets.

Glass blocks can also enhance the safety of a structure. “One reason you’d use glass blocks instead of just a window is that you’re trying to achieve a fire rating,” Buck says. “That means we can utilize them in places where you wouldn’t otherwise be able to put a transparent material.” Swartz echoed that point, explaining that their fire-separation properties were one of the original reasons glass blocks came into use. “If there is a fire in your house, glass will just shatter, whereas the glass blocks will last longer.”

Guerin points out that glass blocks share many of the same properties as masonry blocks and can be used, within reason, in a similar way. “There is load-bearing capacity there; there is horizontal wind-loading and, by extension, seismic capacity there to withstand things.” The steel rods incorporated while installing glass blocks help, too.

Maybe the most famous example of using glass blocks for structural integrity can be found within the Maison Hermès, the Japanese headquarters of the luxe French brand, in the heart of Tokyo’s Ginza shopping district. Hermès commissioned Italian architect Renzo Piano in 1998 to build its headquarters in compliance with Tokyo’s stringent earthquake and fire regulations. According to the Renzo Piano Building Workshop, “the glass block facade is designed to act like a curtain in the event of an earthquake, allowing it to move via the flexible seals between the blocks by as much as 4mm, absorbing rather than resisting seismic shock.”

From Maison de Verre to Soho sidewalks, glass blocks have an architectural history that is more cutting-edge and timeless than their 1980s reputation might suggest. “Glass blocks, in my mind, [aren’t 1980s Miami]; they’re early modernist in 1930s Paris,” says Guerin. “Good design grows out of historic appreciation.”

And besides, “the blocks are cool,” says Swartz. “They’re this really old product that has been reused in a more beautiful, modern way.”