It was an unseasonably hot Saturday in April, and the three dozen terrariums on display in a booth at the Brooklyn flea market were sweating, the moisture turning into beads on their glass containers. Katy Maslow and Michelle Inciarrano, who were selling the miniature gardens, answered questions from passers-by. An antique magnifying glass sat nearby, for those who wanted a closer look. Some of their creations have an irreverent sense of humor: small verdant worlds that feature scenes like muggings, complete with tiny shadowy scoundrels. Others are simpler, more elegant arrangements of stones and mosses. The two friends, who spend most of their weekends 'antiquing and junking,' Maslow said, use repurposed vessels like old apothecary jars, cake stands and decanters to make the terrariums, which seemed at home among the vintage furniture and clothing and artisanal food at the market in the Fort Greene neighborhood of Brooklyn. Inciarrano, a 33-year-old photography student, was the one with the green thumb, who suggested they fill their finds with plants and figurines, said Maslow, 31: 'I had not thought of terrariums once in my whole life.' But in less than a year the pair had created so many, each working in her Brooklyn home -- Inciarrano, in the Marine Park apartment she shares with her husband, and Maslow, in the bright, modern two-bedroom she owns with her siblings in Midwood -- that they decided to sell them, calling the enterprise Twig Terrariums. 'The fine art side of us is totally satisfied by this, and the craft side too,' said Maslow, who holds a bachelor's degree in creative writing and maintains a website for a family business in the entertainment industry. 'I like designing little worlds.' Long a fixture of elementary school classrooms, terrariums have recently begun gaining favor with young design enthusiasts and creative types. But today's look nothing like the fish tank structures and kitschy miniature greenhouses that were popular in the '70s. These terrariums marry the current rage for Victoriana with the growing interest in handmade crafts and all things do-it-yourself. Add to that a touch of locavore fervor, as more urbanites take to terraces and fire escapes to grow flowers and herbs in pots. Grace Bonney, the founder and editor of the blog Design Sponge, said she gets inquiries about terrariums -- how to build them, where to buy them, which plants work best -- every day. In her own home, she has three. 'Terrariums are coming on the tail end of the cabinet of curiosities trend we've been seeing for the past few years,' Bonney said. 'But they also touch on a few other movements: budget-friendly decor and gardening. I've seen more and more of my readers becoming interested in gardening, but they want to start off slowly.' Part of the appeal of building a basic terrarium is that it does not require a great deal of gardening know-how. While regular house plants can demand considerable attention, terrariums offer a bit of nature -- and the sense of calm it can confer -- in a contained, easy-to-care-for way. And once a closed terrarium reaches a state of equilibrium, in which there is neither too much moisture in the container nor too little, it can more or less sustain itself. 'Having these in my home has changed the way I feel about my home,' said Inciarrano. 'It feels more peaceful and in order.' Like Maslow and Inciarrano, Tanesha Smith-Wattley, 31, sells terrariums at the Brooklyn Flea, though she skips figurines in favor of found objects -- a sake cup, say, or a piece of driftwood. Smith-Wattley, a fashion stylist for the website Bluefly, said she came up with the idea of making terrariums when she was searching for centerpieces for her wedding, held last September. She had never done anything like it before, but 'right or wrong, I thought, 'I can make these,' ' she said, relying on her design skills. The leftover materials from the wedding became the terrariums she sold at the flea market, under the name New World Terrariums. She now makes them for events too, and sells them through a store called Task in Williamsburg, creating compositions in containers she buys from suppliers in the flower district, Target and T.J. Maxx. Still, Smith-Wattley describes herself as 'just a girl sitting in my living room' making terrariums. The artist Paula Hayes, on the other hand, could be considered the high priestess of terrariums, having elevated them to objects of art with her exquisitely cultivated creations in custom-made, hand-blown glass vessels. Describing them as 'primordial,' she theorized that terrariums appeal to the human desire to nurture living things. 'It's this beautiful little world you can care for in your apartment because you probably can't go buy a piece of land,' said Hayes, who lives in Brooklyn. The precursor to the terrarium, was devised in 1829 by Nathaniel Ward, a physician by trade and an enthusiastic botanist, who noticed that a fern he was growing in a jar was flourishing, sealed off from the polluted London air. So innovative was his discovery -- and so useful in the age of sea travel, for it allowed for Europeans to bring tropical plants home with them on voyages in which fresh water was scarce -- that the Wardian case was displayed at the Great Exhibition in London in 1851, holding a fern that had not been watered in 18 years. Nowhere is it more apparent that Ward's scientific instrument has become something primarily aesthetic -- and a fixture on the design scene -- than at the downtown creative studio and storefront Partners & Spade. The terrarium on display there, a collaboration between the landscape designer Lindsey Taylor and the Brooklyn firm Atlas Industries, is a large glass cube on a metal stand, a prehistoric landscape contained in the most modern of forms that sells for $9,500. Anthony Sperduti, a partner in the business, said: 'People are blown away by it. One said they wished they could live inside it, it was so bucolic.' Those who can't afford such high-end design -- or would rather make it themselves -- can often be found at Sprout Home, a serene garden store in Williamsburg, Brooklyn, an offshoot of a Chicago store. On a recent afternoon, a long-limbed young woman clad in leggings and a cardigan with the look, if not the provenance, of a vintage-store find, approached the counter carrying a cloche. The glass was smudged with thumbprints, suggesting that the jar had been handled by an untold number of admirers at a flea market before she bought it. She asked for help creating a terrarium, telling the woman behind the register, 'I've never made one before, but I looked it up on the Internet and was totally obsessed.' Tassy Zimmerman, one of the store's owners, said that several such customers come in every day asking about them. 'There is definitely a huge craze,' she said. A YouTube video of Zimmerman demonstrating how to make a terrarium has been viewed almost 24,000 times since it was posted on Design Sponge; by comparison, Bonney said, the average video on the site that is not part of an ongoing series garners about 10,000 views. In addition to offering classes and pre-made terrariums priced between $50 and $250, Sprout sells the materials for constructing one -- which come with a step-by-step instruction sheet (also available on the store's website) -- and accessories like miniature feathered birds and crystals. Zimmerman said she had a handful of customers who had been inspired to hold terrarium-making parties after watching the video on Design Sponge, buying soil, charcoal and rocks in bulk. Flora Grubb, a landscape designer who owns the 28,000-square-foot nursery Flora Grubb Gardens in San Francisco, said her average terrarium customer is a little younger than her typical client, and is not generally an avid gardener. 'It's a design-y set,' Grubb said. 'They are interested in plants from a design standpoint, not a horticultural standpoint.' Many are drawn in by the creative aspect -- deciding whether to make a tropical terrarium, for example, or one of 'the really artistic terrariums,' she said, which 'take an artistic hand to make.' In the last year, she said, the best-selling item in her online store has been a kit for building a terrarium in a small glass bubble. 'We sold a gazillion of them,' she said. One of Grubb's customers, Katie Goldman Macdonald, 26, is a women's apparel designer for Old Navy with a special fondness for succulents. Macdonald grew up around plants -- her father has a master's degree in botany -- and has made around 100 terrariums over the years. She has sold about 40 of them in the past eight months, she said, and posts pictures of them on her website, botanyfactory.com. Macdonald has her ovoid glass containers hand-blown in Oakland, Calif., and builds her terrariums in her plant-filled studio apartment in the Mission District. Her sleek creations, filled with the architectural, slightly alien shapes of her succulents, would not be out of place in a room furnished with midcentury modern pieces. She described making a terrarium as a sort of science experiment, albeit one conducted with color, texture and visual composition in mind. 'They fit with the current infatuation with all things old and scientific,' she said, 'and this Victorian idea of science as beauty and something you want to display in your home.' Macdonald initially made some terrariums to sell at a craft fair at work, figuring that her colleagues, who are 'obsessed with aesthetics,' she said, 'would be fascinated with having beautiful arrangements in their home that they can look at and not have to do much to.' That is one of the main draws of terrariums, she said: They are good for people who love plants but do not actually enjoy gardening. 'There are those people who go to Marin and hike on the weekends, but I think people live in cities because they are city people,' she said. 'I tried to start a garden on a city farm for a while, but I realized that I am not really an outdoorsy nature person,' she added. 'Terrariums are a way to be connected to that while staying indoors.' 