You may have passed Just Shades while on a stroll through NoLita and wondered how the shop, which seems to have been there forever, has survived various economic conditions throughout the decades by selling nothing but lampshades. 

More puzzling is that it lives in a neighborhood where one-bedrooms rent for $3,000 a month on average, and classic downtown staples like Pearl Paint and J&R Music and Computer World have shuttered at an alarming pace.

Just Shades first opened at a different location in the early 1960s and has been at 21 Spring St. for more than 40 years. It also has a storefront in Greenwich, Connecticut.

We spoke with its current owner Marc Engelson, who runs the business with his wife Bonnie, to find out the store's secret to longevity. His answer: a stronghold in a niche market.

"I'm one of the only ones left, because it takes a lot of inventory and a lot space," Engelson said of lampshade stores.

He cited two uptown spots, Oriental Lampshades and Gracious Homes, but they sell whole lamps, not just shades. "If there was one of us on every other corner I'd be saying, 'time to fold up,'" he said. "But we're still in business."

And business is good. This isn't just any old lampshade store, after all -- it has a bit of fame.

Engelson has seen the likes of Maggie Gyllenhaal, Liv Tyler, Glenn Close, Matt Dillon and Lena Dunham -- who Instagrammed a picture of herself inside the store -- pass through its doors. There was also David Letterman's famous "Late Night" clip in 1983 that comically featured Just Shades and Just Bulbs.

The store has sold 6,000 lampshades so far in 2015 and aims to sell 13,000 this year, Engelson said. Its busy season is from February to June and September to November, he noted, when people tend to redecorate their homes.

Its unique shades have also been in several movies and TV shows, including "Spiderman," "Sex and the City," "The Sopranos" and "Boardwalk Empire," but Engelson added that the big screens only contribute 7-10% of the store's business a year.

"All the set designers know us," he said. 

Right now the shop is offering some throwback styles from the '60s and '70s; the stick shade ($280) is the hot ticket item at the moment.

"Introducing things like this has always kept us ahead of the game," Engelson said of the shade.