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Last week, Gagliardo watched as workers pulled an Australian tree fern off of an Amazon Prime truck, carried it through a particularly wide door in one of the spheres, and plopped it into the soil. Australian tree ferns are hardy, primordial plants that can reach 50 feet tall and “a favorite among greenhouse staff,” says Gagliardo. This particular specimen spent three years growing in Amazon’s conservatory at the edge of town. It is the first of the 40,0001or so plants destined for the domes, which open next year.

Maybe it’s all the screen time or mounting evidence that employees excel when surrounded by nature, but tech companies suddenly love plants. Airbnb installed a living wall in the lobby of its San Francisco headquarters. Apple wants a small forest of 8,000 trees at its new campus in Cupertino. Adobe incorporated biophilic design into its offices in San Jose, California. Yet they all pale compared to Amazon and its three conjoined spheres, which are both meeting rooms and conservatories that will house more than 400 species of rare (and non-rare) plants.

When Amazon began building its new campus five years ago, it insisted on incorporating nature in the design. Employees can open windows windows in Doppler, the 38-story tower downtown. Plazas teeming with trees dot a campus of 30 buildings. Dogs romp in a park designed just for them. And then there are those spheres, designed to bring the outdoors indoors within the confines of an office building. “The question was, how do we do this in a significant way,” says Dale Alberda, a principal architect at NBBJ, the firm behind Amazon’s new campus. “Just bringing plants into the office wasn’t going to cut it.”

The designers explored hundreds of shapes before choosing spheres. “It’s the most efficient way of enclosing volume,” Alberda says. The domes, made of glass panels on a steel frame, create enclosed biospheres that combine work and nature. That created a challenge, though, because plants and humans like different things. Plants thrive in warm, muggy environments. Humans do not. Amazon may love nature, but it still needs productive employees, so it compromised: The domes remain a pleasant 72 degrees with 60 percent humidity during the day, while at night they’re a more plant-friendly 55 degrees with 85 percent humidity.

“It’s people first,” says Gagliardo. “Then we figured out what plants we could put around people.” Gagliardo started with plants found in similar climates. Mid-elevation regions like the cloud forests of Ecuador, Costa Rica, and parts of China fit the bill. A crew will carefully crane a 60-foot tree from California into the domes next month. Once gardeners and horticulturalists plant everything, the dome and its 60-foot living wall will house vegetation from more than 50 countries.

Some of those plants, like moss, ferns and calatheas, have no problem with low light. Others, like the African aloe tree, require full sun. The architects shunned the triangular panels you may know from Buckminster Fuller’s famed geodesic dome in favor of the five-sided panels of a pentagonal hexecontahedron. That resulted in larger panels, which allows more sunlight into the sphere. Ninety LED fixtures with light sensors provide additional lighting when necessary.

All those plants need a lot of water, a task Gagliardo prefers to do by hand. “The collection is so diverse that putting everything on automatic sprinklers would be really difficult,” he says. Each day his team of horticulturists will wander the domes amid executives taking walking meeting and office drones doing whatever Amazon’s office drones do, tending to plants and rooting around in the dirt. “It’s a dream job,” Gagliardo says. “I never would have thought I’d be here at Amazon doing horticulture.”

1UPDATE 11:55 AM ET 05/6/2017: This story has been updated to accurately reflect the number of plants in Amazon’s Spheres.