More than a cryptocurrency, Bitcoin is really a set of rules à la SMTP, the protocol that makes email work. The possibilities for innovation around Bitcoin’s block chain—the public ledger on which every Bitcoin transaction is recorded, like a library card in the cloud—are exciting. The block chain allows for any exchange of value between two entities without a middleman. Transactions of all kinds are possible. You can use the block chain to store documents securely. Onename, a startup, is working on a social network that uses the block chain to validate identity. (Sorry, Facebook.) And then there’s the Internet of things. “Every time you’re running low on printer ink, it could notify the block chain and send you more,” theorizes Ryan Selkis of the Digital Currency Group.

Prepare for a new kind of Bitcoin boom.

This story is from the January 2015 issue of Fortune.

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