Tsien, 61, AIA, and Williams, 68, FAIA, have been working together for more than 30 years. Williams hired Tsien in 1977; he was her first employer. Williams and Tsien formed a full partnership in 1986, five years after the practice moved into a ground-floor space on Central Park. “Within a very short period of time, I realized she was the best thing I could ever have,” Williams says.

The studio expanded in 2000, assuming space formerly used by photographers. “The designation was residential and commercial,” Williams says. “Starting in 1981, we could only get a residential mortgage, because we couldn’t prove anything.”

Many of the firm’s 30 employees bike to the studio, which has three showers and a full kitchen.“To me, it’s not so different from the kind of studio atmosphere you have in school,” Tsien says. “We interview people because we want them in the studio. They come understanding that.”

Williams and Tsien are “by far” the oldest people in the studio, though they all work in the same space. “We’re kind of like the parents,” Williams says. (Tsien strenuously disagrees.)