SEEING THINGS.

One cool wet afternoon at the end of April, a dozen people stood in a round, foil-lined room in the Tanya Bonakdar Gallery, in Chelsea, looking at a large piece of black plastic. Most of them were young, their clothes were splattered with white paint, and their faces registered equal parts exhaustion and consternation. They murmured to one another in German. A few yards away, through the open door of the freight entrance, rain blew in. The opening of a show by the Icelandic artist Olafur Eliasson was in less than twenty-four hours, and the major piece--a circular wooden pool, a foot deep and eighteen feet across--was proving problematic: the black plastic lining was bunching up and drifting. It looked as if a small pilot whale were breaching the surface.

Eliasson stood apart from the group. As a teen-ager, he was the break-dancing champion of Scandinavia; at thirty-nine, he is a physically economical man of few gestures, one of which is to push back a forelock of rusty brown hair which often falls into his face. Dressed in bluejeans, a white shirt, and an anorak, Eliasson had the slightly crumpled look of a shop teacher at a progressive school. His glasses were fogged. He said, "This needs to hold water in twenty-four hours. Any ideas?"

This was Eliasson's tenth-anniversary show with the gallery, and he stayed in New York for a week to oversee its installation--a testament to his regard for Tanya Bonakdar, a precise, elegant En-glishwoman in her early forties, who manages almost all aspects of his career. ("Tanya and I grew up together," he says.) He had come with five assistants from East Berlin, where, in a studio housed in an old train depot, he employs up to forty people, including mathematicians, technicians, carpenters, and architects, most under the age of thirty-five. Daniel Birnbaum, the director of the Stadelschule art academy, in Frankfurt, some of whose students have gone on to work for Eliasson, describes the people he picks as "brilliant" and "crazy."

This year, Eliasson has had twelve solo shows around the world. His best-known work is "The Weather Project" (2003), an installation in the vast Turbine Hall of the Tate Modern, in London, which consisted of a gigantic half sun--made of hundreds of light bulbs--at the top of one wall, mirrors on the ceiling, and a mist machine. Rather than trying to minimize the space, Eliasson doubled it: the mirrors created the top half of the sun and extended the space vertically, while the mist, pumped into the hall at regular intervals, refracted the light and, like London fog, made distances between points curiously unfathomable. The effect was what one critic called "a romantic indoor weather scene." Open for six months, it was visited by more than two million people. Next fall, the San Francisco Museum of Modern Art will mount a major survey of Eliasson's work, titled "Take Your Time: Olafur Eliasson," which will then travel to New York, to the Museum of Modern Art, with an annex of the show at P.S. 1, in Queens. Madeleine Grynsztejn, SF-MOMA's chief curator of painting and sculpture, met Eliasson in Berlin in 1997. "He had a little studio space. He had a few four-by-five photographs of men fishing in Iceland," she recalled. "It was clear to me at that moment that Olafur represented immersion in experience. You could feel the cold in your fingertips."

Later that day, in Chelsea, I sat with Eliasson at a diner on Tenth Avenue. He speaks Icelandic, Danish, German, and English; in English, his voice is measured, colloquial, and lilting. He said, "A show like this comes out of the laboratory. It's not about foil and water. It's about how we feel about those things. The pool is a machine that can produce a phenomenon, but I'm very aware that it can come close to being a setup." His genial features sharpened. "Working on the idea of experience is something in-timate. Speaking with you, now, will change the way I see when I return to the gallery." He called the Chelsea show "Your engagement sequence," or "YES." (For a number of years, he has used the word "Your" in his exhibition titles, to emphasize the primacy of the viewer's experience.)

In Berlin, Eliasson discusses all works with his staff--when I met him last spring, there were more than fifty potential projects on his list. A design for a thirty-foot-high double-spiral staircase, shaped like a Mobius strip--you enter it at the bottom and walk up and down in a continuous loop--which is on permanent display in a courtyard in Munich, necessitated, by Eliasson's estimate, more than a hundred conversations with Sebastian Behmann, the chief architect in the studio. To Eliasson, those talks--in which they considered the idea of what a stair might be, the history of stairs, the expectation of where a stair might lead--were part of the finished piece.

Eliasson invites comparison to Buckminster Fuller, with whom he shares an interest in the aesthetics and the utility of mathematical forms, and to the artists Robert Irwin and James Turrell and the idea of "seeing yourself seeing." Like them, he is interested in light, to which he adds a preoccupation with what he calls "the intersection of nature, science, and human perception." But unlike those artists, who tend to draw the viewer's attention to natural phenomena--Turrell's "sky spaces," for example, showcase the open sky--Eliasson consistently uses mechanical artifice to create his effects in art interventions, photographs, installations, and exhibitions that are often more like optical experiments than art shows.