Of the more than 100 related chemicals found in cannabis plants, cannabidiol (CBD) has become almost as well-known as tetrahydrocannabinol (THC), seemingly overnight. Now widely available in retail stores and websites, it has suddenly emerged as a popular consumer product.

But it has been difficult to demonstrate exactly what CBD does. It neither produces a high like THC, nor does it have the same biological actions. And although promoted as a remedy for a wide variety of conditions, only one CBD product has received FDA approval—for the treatment of a specific type of severe childhood epilepsy.

Much remains unknown about the effects, mechanism, long-term consequences and legality of CBD. Join Steven Grant, a neuroscientist at the National Institutes of Health, for an examination of what research has—and more importantly, has not—discovered about this elusive chemical's potential benefits and risks.