Headquarters: San Francisco, California
Year founded: 2009
Why it's revolutionary: Online thrift store ThredUp is leading the way in the secondhand buying-and-selling market. It's now the largest online secondhand store and has four stores in the US.
Customers selling unwanted items are sent a "clean out bag," which they send back to ThredUp to decide what can be sold and what will be donated. The seller is either paid upfront or on consignment.
Cofounder James Reinhart told Business Insider that the store has 35,000 different brands and that fresh inventory and a wide selection are what keep customers coming back for more.
In October, ThredUp launched UPcycle, a program that enables customers to donate clothing and turn it into cash to spend at trendy brands such as Reformation.