From 1960s Korea, through Brazil, to today’s Los Angeles: Inside the world that brought you Forever 21—and those skinny jeans in your closet.

Over the past 15 years, the fashion industry has undergone a profound and baffling transformation. What used to be a stable three-month production cycle—the time it takes to design, manufacture, and distribute clothing to stores, in an extraordinary globe-spanning process—has collapsed, across much of the industry, to just two weeks. The “on-trend” clothes that were, until recently, only accessible to well-heeled, slender urban fashionistas, are now available to a dramatically broader audience, at bargain prices. A design idea for a blouse, cribbed from a runway show in Paris, can make it onto the racks in Wichita in a wide range of sizes within the space of a month.