It's been used to buy drugs. Guns. Child porn. And to launder money.
But high-profile institutions like the World Bank, UNICEF and USAID think it could be a force for good, helping the poorest of the poor.
It's a technology called blockchain — a global, online ledger that's free for anyone to use and that isn't regulated by any one party.
Maybe you've heard of it. And maybe you don't know exactly what it is.
That's because it's not easy to define.