Rick Simpson Oil, called RSO for short, is one of the most versatile and lauded cannabis innovations—an oil created by Rick Simpson, a Canadian engineer and cannabis advocate who was radicalized to cannabis activism by a work accident that led to various health issues. The story goes that he was able to resolve his health issues with RSO, a dark, tar-like cannabis extract that straddles the line of concentrate, edible, and topical. In short: There’s very little it can’t do, and a lot it can do for both patients and stoners.