Snapchat's journey from start-up to tech giant

Snapchat co-founders Evan Spiegel, Bobby Murphy and Reggie Brown came up with the idea for the app as students at Stanford University. Over the next several years, Snapchat grew into a multi-billion dollar company. Billy Gallagher, author of "How to Turn Down a Billion Dollars: The Snapchat Story," joins CBSN to discuss his new book about Snapchat's history.


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