Attending Euroluce, the most influential and trendsetting decorative lighting show, has always meant preparing for a heat wave. At the huge fair (this April, 479 exhibitors inhabited 445,508 square feet of space), the temperature has always increased throughout the day, thanks to the heat generated by all those lamps in an enclosed area, until visitors would feel as if they had been dropped into the middle of the Sahara. But this year, the air at this biennial show—which alternates years with a kitchen-and-bath exhibition during Milan's famed furniture fair, Salone Internazionale del Mobile, at the Rho fairgrounds—was positively springlike.

The reason for this temperature change doesn't require the skills of a climatologist to figure out. It is occurring because lighting manufacturers, including companies who specialize in decorative lighting, have switched over en masse to LEDs. They are forsaking incandescent lamps as lighting technology undergoes a paradigm shift and legislation around the world mandates the use of more energy-efficient products. Frosted incandescent lamps have already been phased out of production and sale in the European Union. By the end of 2012, just about all types of general-purpose incandescent lamps also will be off the market there. These laws clearly have had an effect on manufacturers—European and worldwide. “Of the 55 SKUs that we introduced, 50 of them are LEDs,” says Jan Vingerhoets, CEO of Flos USA. “LED is the future.”

Murray Moss, co-owner of New York–based Moss, an influential American design store, agrees, but thinks that it isn't legislation that's behind the change. He believes that people are starting to get used to this new technology, which, he points out, designer Ingo Maurer was already working with more than 10 years ago. “Smart people will take it up, and it will evolve to other forms,” he says. “This is just the beginning. But it's irreversible now.”

The change to LEDs dictates a new design vocabulary. The predominant silhouette at the show was long, lean, and tubular, showcasing the beamlike quality of the tiny lamps—although there was also the usual number of perennially popular globelike forms on hand. Ingo Maurer brought to market his LED wallpaper, a product he's been working on for several years. (Pricing is available on a special project basis.)

There were, of course, some holdouts. Artek's new White collection—a series of four linear lighting solutions designed by the company's design director Ville Kokkonen—does not use LEDs. Instead, Kokkonen opted for T5 fluorescents, which are still an extremely cost-effective and functional light source.

There were also pioneers who moved on to the next big thing: OLEDs—organic light-emitting diodes—which are still very much in the experimental stage. Blackbody, a French company dedicated to developing OLEDs for both residential and commercial use, had a large booth with a wide range of products, from tasklights to chandeliers. Kaneka, a Japanese firm that exhibited off the fairgrounds, created a visual wonderland of small, floating OLED forms in a dark mirrored room.

Outside of the fair, there was much, much more. From company showrooms on the chic shopping streets around San Babila to the design districts in Zona Tortona, Brera, and the latest hot neighborhood—Ventura Lambrate, the area of choice for the young avant-garde—an embarrassment of riches awaited. The legendary Venini, the Murano-based Venetian glass and lighting company, celebrated its 90th anniversary with an exhibition at the Museo Bagatti Valsecchi. (The pieces, including new designs by Studio Job and the Campana Brothers, were dramatically juxtaposed with the museum's rich collection of Italian Renaissance decorative arts.) Dutch studio Drift lit up the Lambrate neighborhood with its ghostly Fragile Future fixtures, made from dandelion seeds (yes, dandelion seeds), LEDs, and bronze. And, on the Via della Spiga, the Nilufar Gallery showcased the ethereal glass totem lamps of Bethan Laura Wood, a young Englishwoman and former student of designer Martino Gamper.

Every year the number of exhibitions and special events outside the fairgrounds expands exponentially—there is no longer any way to visit all of them. During this special week, Milan is a design lover's paradise. If you didn't make the journey this April, there's always 2013. Put it on your calendar.

Design journalist Arlene Hirst worked at Metroplitan Home magazine for more than two decades as senior editor and then as deputy design director. She currently contributes to T, The New York Times Style magazine, as well as to Surface, Interior Design, and Elle Décor Italia.