How two friends formed Amazon's first U.S. union and what's next

When more than 2,600 workers at a Staten Island, New York, warehouse voted to join Amazon's first U.S. union in April, it was a historic moment. But it was only the first step in a long uphill climb toward a contract. Amazon filed 25 objections to the win and five weeks of hearings concluded this week. CNBC sat down with Amazon Labor Union co-founders Chris Smalls and Derrick Palmer to learn about their battle and find out what happens next if the National Labor Relations Board upholds the union.