Making marijuana into a legitimate business
Cannabis has been legal for recreational use in the US states of Washington and Colorado for more than a year now.
Voters have also backed legalisation in Alaska and Oregon, and are facing a new challenge - how to turn an illegal drug into a legitimate business.
Alastair Leithead has been to Seattle - to see how legal cannabis is going, and over the border to Salem, Oregon - to see how they are planning to implement it.