Cannabis is probably one of the first plants that humans cultivated and has a rich and varied history as a medicine, spiritual aid and for its rope-making hemp fibres.
It has also been outlawed and criminalised in many countries, but as the full effects of the so-called war on drugs have become clear, public opinion has started to change in favour of legalisation.
While cannabis is currently enjoying a renaissance as a medicine and even a craft product in some US states that have legalised it, there is still a dearth of hard scientific knowledge around the drug.
This is largely because researchers have been unable to get the quality cannabis they need for studies, due to overregulation.
Now, however, a new breed of ultra-nerdy legal growers is helping scientists to learn more about the drug, and how different compounds in the plant can interact to provide different medicinal effects.
This article explores the history of cannabis use, and some of the mysteries that are only just being discovered today.