For thousands of years, cannabis was seen as a mysterious, sacred, even demonic plant. Today, weed is hugely popular. You can buy hundreds of strains, specially cultivated to produce different flavors and highs. You can buy it in vape cartridges and gummies and brownies. And it’s a lot stronger than it used to be: more than three times as potent as it was in the mid-’90s.

But, since it’s still illegal in most places, it’s also almost entirely unregulated. There is no “standard unit of weed.” Strain names like “Pineapple Express” or “Candy Cane” don’t tell you much about the product you’re buying.

So how did humans engineer this ancient plant into the drug it is today? And what does all that uncertainty mean for a booming marijuana market and its customers?

Vox tackled this question in this week’s episode of our Netflix show, Explained. We have new episodes every Wednesday on topics ranging from the racial wealth gap to dieting and more. If you like our videos, then you’ll love this show; it’s our most ambitious video project to date.

To watch, search “Explained” on Netflix or go to Netflix.com/explained. Click the “My List” button to make sure you don’t miss an episode.

Learn more:

The benefits and harms of marijuana, explained by the most thorough research review yet (German Lopez, Vox)

Weed is not more dangerous than alcohol (a video by Vox’s Ezra Klein and Joe Posner)

How to prevent casual pot smokers from slipping into abuse and dependence (Mark A.R. Kleiman, who we interviewed for this episode, writing for Vox)

Why is weed getting more potent? (Bucky Turco, Gizmodo)

Seeing green: Celebrities selling marijuana (This CBS news piece looks at celebrities entering the legal weed business, featuring actor Tommy Chong, who we also interviewed for this episode)

The evolution of hemp and marijuana (Botany of Desire author Michael Pollan, who we also interviewed for this episode, discusses the history of cannabis with PBS)

This Professor Teaches About Drug Use, Including His Own (A WNYC interview with Columbia neuroscientist Carl Hart, who we also interviewed for this episode)

Why Chocolope? To sell marijuana, you need a clever name (A Los Angeles Times story about cultivating and marketing marijuana strands featuring Adam Orenstein — also known as “Kyle Kushman” — who we also interviewed for this episode)

Developing Public Health Regulations for Marijuana: Lessons From Alcohol and Tobacco (a report co-written by economist Rosalie Pacula, who we also interviewed for this episode)