As more states, including Minnesota, allow limited use of marijuana for medicinal purposes, scientists are expanding research efforts to understand how marijuana and the chemicals it contains interact with the body.

Hampton Sides wrote about the science of marijuana in the June issue of National Geographic. He joins MPR News' Tom Crann Wednesday at 9 a.m. to talk about his piece.

What scientists know about marijuana

Israeli organic chemist Raphael Mechoulam found marijuana's principal active ingredient: tetrahydrocannabinol (THC)

From National Geographic:

One day in 1963 a young organic chemist in Israel named Raphael Mechoulam, working at the Weizmann Institute of Science outside Tel Aviv, decided to peer into the plant's chemical composition. It struck him as odd that even though morphine had been teased from opium in 1805 and cocaine from coca leaves in 1855, scientists had no idea what the principal psychoactive ingredient was in marijuana. "It was just a plant," says Mechoulam, now 84. "It was a mess, a melange of unidentified compounds."

Researchers know very little about the medical benefits of marijuana because it's classified as a Schedule 1 drug. But the government is showing signs of loosening restrictions on research.

From National Geographic news:

One way to gauge their thinking is to look at what's going on at the University of Mississippi, the site of the only cannabis farm sanctioned by the government. The facility is overseen by the National Institute on Drug Abuse (NIDA), which places orders for strains it wants for research. Last month, the DEA signed off on a NIDA request to more than triple federal marijuana cultivation from its previously stated 2015 quota of 276 pounds (125 kilograms) to 881 pounds (400 kilograms), explaining that "research and product development involving cannabidiol is increasing beyond that previously anticipated."

Parents are using compounds from medical marijuana to treat serious conditions in their children

Pharmaceuticals are interested in marijuana, but it's tough to make money off the plant.

"You can't patent marijuana," Sides told KPCC. "It's just a weed. It grows everywhere."

Companies like GW Pharmaceuticals are focusing on isolating individual compounds and slightly altering it chemically so they can patent and mass produce it.

Some research shows promise for brain tumors, but it's only been tested on animals.

Biochemist Manuel Guzman's research:

On his screen flash two MRIs of a rat's brain. The animal has a large mass lodged in the right hemisphere, caused by human brain tumor cells Guzman's researchers injected. He zooms in. The mass bulges hideously. The rat, I think, is a goner. "This particular animal was treated with THC for one week," Guzman continues. "And this is what happened afterward." The two images that now fill his screen are normal. The mass has not only shrunk--it's disappeared. "As you can see, no tumor at all."

Scientists are trying to map the marijuana genome. Right now, it's in 60,000 pieces.

"Once the map is complete, enterprising geneticists will be able to use it in myriad ways, such as breeding strains that contain much higher levels of one of the plant's rare compounds with medically important properties," Sides writes.