Sneaker, trainer call them what you will. How did this product of the industrial revolution and a rising middle class become a global fashion item worth tens of billions of dollars a year? Especially when 85% of the purchases are never intended for its original purpose, health and fitness. Join Mike Williams for the Why Factor on Sneakers.

Produced by Julie Ball

(Photo: A man looks at a collection of sneakers in the window of a shopping mall, in the outskirts of Sao Paulo, Brazil. Credit: Getty Images)