What if there were a rolling paper that let you put the entire marijuana industry into a tightly packed joint? There is, and it's called an exchange-traded fund.

While more and more states legalize medical and recreational marijuana in the U.S., the federal government still classifies it as an illegal controlled substance. But that certainly doesn't make it illegal to invest in the industry, and certain publicly traded companies in the sector have seen their valuations soar of late. Most of these companies also happen to be based in Canada, a country that just legalized recreational marijuana last month. 

Bloomberg News reporter Rachel Evans takes a field trip to Toronto for a closer look of the nascent industry and a better understanding of the ETFs investors are using to gain exposure. She also joins Eric and Joel to discuss why investors should proceed cautiously in such a seductive space.