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The rise of bitcoin

Bitcoin is an experimental digital crypto-currency unregulated by a central bank where its value -- like many real-world currencies -- is determined by how much people are willing to use it. Here, software engineer Mike Caldwell of Sandy, Utah holds physical Bitcoins he minted in his shop in April this year.

Bitcoin is an experimental digital crypto-currency unregulated by a central bank where its value -- like many real-world currencies -- is determined by how much people are willing to use it. Here, software engineer Mike Caldwell of Sandy, Utah holds physical Bitcoins he minted in his shop in April this year.