This article was originally published in Fortune.

“Nostalgia, it’s delicate but potent,” said Mad Men’s Don Draper as he pitched a concept for Kodak slides. In his famous speech that aired in late 2007, just as Wall Street banks were beginning to wobble under the weight of mortgage-backed securities, the iconic advertising executive described why brands look to the past.

“Nostalgia,” he said, is a Greek word that means “the pain from an old wound, it’s a twinge in your heart, far more powerful than memory alone,” as he scrolled through pictures of his blissful family in the New York suburbs. “It takes us to a place where we ache to go again,” he said to a spellbound boardroom.