Marijuana is now legal in some US states and a fast-growing industry has emerged, especially in Colorado which was the first state to embrace the drug. But according to federal law marijuana is still illegal. This means that many companies can't get banking services, advertise their wares or pay tax in the way that other companies do. So how do they survive and thrive? And in what direction is the US moving? Will marijuana soon become a legal drug, like alcohol, across the US? Or will law-makers decide that Colorado's big marijuana experiment has gone too far? And what is it like to run a company in one of the world's riskiest business sectors? Presenter : Peter Day Producer : Rosamund Jones.