Neiman Marcus is testing a digital "Memory Mirror" that lets shoppers see how an outfit looks in back as well as displaying items they've tried on side by side. Courtesy of Neiman Marcus hide caption

itoggle caption Courtesy of Neiman Marcus

Workers pack items Sunday at an Amazon fulfillment center in Tracy, Calif. Cyber Monday online sales jumped 8.5 percent over 2013. Noah Berger/Reuters/Landov hide caption

itoggle caption Noah Berger/Reuters/Landov

Customers walk out of Street Boutique, parked in Shirlington Village, Va. Street Boutique is a pop-up truck that's similar to the many food trucks in the area, except it sells clothes and jewelry. James Clark/NPR hide caption

itoggle caption James Clark/NPR

Lenox Mall, in the Buckhead neighborhood of Atlanta, used to be the site of a country home estate and is now a traditional indoor mall with two anchor stores. Madeline Veira/Youth Radio hide caption

itoggle caption Madeline Veira/Youth Radio

A Nordstrom salesperson shows a customer an online selection of shoes on an in-store iPad. Like some other retailers, Nordstrom is using mobile devices to make on-the-spot sales and check companywide product inventory instantly. Courtesy of Nordstrom hide caption

itoggle caption Courtesy of Nordstrom