The man considered the world’s foremost marijuana researcher began studying cannabis scientifically in the 1960s. He was not a hippie.

Dr. Raphael Mechoulam, 86, is now a professor at Hebrew University in Jerusalem and an advisor to the Israeli government’s medical marijuana program. He has never smoked a joint. But he’s been deeply curious about cannabis for nearly his whole professional life—starting as a young researcher in Israel, when almost nothing was known about the plant and its medicinal potential.

“I’m a chemist,” Mechoulam recently told Culture magazine. “I work with natural products, and I was looking for something important in natural products in plants, and I was surprised to find that while morphine had been isolated from opium nearly 150 years previously and so was cocaine from coca leaves, the chemistry of cannabis was not well known, and I thought it was a good topic to do research on.”

Getting started was difficult, however. His first experiment was conducted with hashish—a cannabis plant extract—obtained from a police evidence locker through a contact. This approach to obtaining weed turned out to be illegal. “But [Israel] is a small country,” Mechoulam explained. “I went to the Ministry of Health and I apologized, and any time I needed more hashish I went [back] and had no problems.”

The chemist is credited with making many of the most important scientific discoveries about marijuana. First, he isolated the plant’s psychoactive component, tetrahydrocannabinol (THC), and an element of cannabis that produces no high, cannabidiol (CBD), which has many medicinal properties. It’s an antioxidant and anti-psychotic; suppresses seizures; relieves pain; and reduces nausea and inflammation, among other benefits.

Mechoulam also identified cannabis receptors in the human body and studied the way plant cannabinoids interact with those receptors. ”The receptors don’t exist because there’s a plant out there,” he said. “The receptors exist because we produce compounds which bind to these receptors, activate them, and cause activities.”

Today, Mechoulam is most curious about those endogenous cannabinoids, the compounds that human and other animal bodies create naturally. These compounds operate in the brain and nervous system, influencing pain, appetite, mood, memory, motivation, and more. He explained to Culture: