AMONG THE WORLD’S top architects, Rem Koolhaas may be the most influential. An energetic teacher—most often at Harvard’s Graduate School of Design—and persuasive writer (his books include Delirious New York and S, M, L, XL), he has also mentored scores of young architects at his Rotterdam studio, the Office for Metropolitan Architecture (OMA), where pay is S and pressure XL. (American architect Joshua Prince-Ramus remembers that his first “day” on the job lasted 48 hours.) But Koolhaas’s apprentices are rewarded with something more than money: Under his tutelage, designers learn to privilege approach over style. Rather than work with drawings, like most traditional architecture firms, OMA employees first “Diagram” a building—identify the structure’s basic components and how they fit together—and then proceed to build it. It’s an analytical method that results in buildings that are sometimes ungainly but never unexciting and reject the signature styles associated with many other renowned architects. “Rem is a magician in terms of the quality of work and thinking he is able to get out of people,” says Amale Andraos, a young Lebanese-born architect who began working at OMA in 1999.