The supply chain of cocaine stretches around our world, bringing vast wealth to a few ... and misery to millions. Follow its trail through the eyes of peasant farmers producing cocaine paste, a trafficker tied to Mexican cartels and a 28-year-old crack dealer in Miami's poorest neighborhood. And literally see the true nature of cocaine addiction via revolutionary brain photography in a leading lab in Brookhaven, N.Y.

Heroin can be life threatening, claiming the lives of numerous victims. Follow this opium derivative as it begins in a remote Afghan heroin lab that processes the raw materials and then on to Chicago, where a dealer demonstrates its final preparation for street sale. Gain insight into its insidious powers from users, and witness a police raid on a heroin distribution network in New Jersey. Plus, go inside one radical attempt to combat heroin's social costs by supplying it free to addicts.

Cannabis is the most widely used illicit drug on the planet. To many, it's an evil weed, but to some, it's a sacred herb, even a lifesaver. For decades the global supply was controlled by criminals, but now a quasi-legal industry worth billions of dollars is booming. Visit growers who are leading a horticultural revolution, hear from users consuming for medicinal purposes, go inside the "Green Rush" of medical marijuana in cities across the U.S. and the violent marijuana cartels in Mexico.

A former British gangster serves as guide into this illicit underworld, visiting a secret hash-making location nestled in the mountains.

Deep in the Amazon, Rob—a former Wall Street broker turned healer—has created a free clinic of sorts, administering the highly potent narcotic ayahuasca to trauma patients.

Auto crime is the tip of a sinister global iceberg where a car stolen in LA could end up on the Russian black market or a truck taken in Laredo, Texas could become a heavily armored 'narco tank' used in Mexican Cartel gun battles.

Alaska has a dark secret : it has one of the biggest drug problems in America. We'll get a firsthand look at the effects of heroin and the withdrawal symptoms involved in using the drug.

In Hawaii, which has one of the highest rates of crystal meth users in the nation, National Geographic Channel cameras follow along on a raid to a drug trafficker's house to discover a woman who continues to deal crystal meth while her husband is in jail.

The devastating consequences of Hurricane Katrina in Louisiana resulted in a wave of small-scale drug dealers taking over the streets of New Orleans. As a means of coping with depression and post-traumatic stress disorder, traumatized locals have turned to cocaine.

Mexican and Canadian drug gangs compete for customers in the isolated terrain in Montana as officers patrol the vast region hoping to stem the tide.

Heroin, cocaine and prescription pills in plentiful supply makes Los Angeles one of the biggest drug distribution hubs in the U.S.

The local drug scene casts a dark shadow on the sunny lifestyle of Puerto Rico, a place where addicts roam the streets in search of their next fix. For Dr. Panelli, treating abusers for jungle rot,Â"a ghastly condition that comes with using injected drugs, can be an overwhelming task.

The most dangerous city in the USA, Detroit, is a perfect mark for today's growing drug industry. Dealers are learning cater to inner city clientele by selling smaller amounts of hard drugs like heroin and cocaine for single-digit prices.

Cocaine and marijuana drug fueled 24-hour lifestyle for Londoners.

San Francisco, Calif. — the epicenter of the 1960s' psychedelic revolution — is notorious for drugs. But in the new millennium, the city, especially the gay community, is struggling to recover from a meth epidemic. The enabler of this situation is the Asian cartel, which has been poisoning San Francisco with high quality meth for almost 25 years — but the Mexican cartels are intent on taking over. Nat Geo goes inside one of the worst drug ghettos in America — the heart of the drug trade.

Kingston is in the hands of highly organized and warring drug gangs. They manage drug trafficking and distribution at all levels. With the patronage of politicians, they fight hard to protect their turf in a city where poverty and guns drive the drug trade.

Houston's drug hub is the 'Bloody Nickel' - the Fifth Ward. Five square miles of 24/7 drug and party action. Gangs work across the ethnic divide to keep the drugs flowing; while cops and Cartels vie with each other for control.

Denver - the mile high city - has just legalized recreational use of Marijuana. The city's gang-banger dealers have battled falling profits since medical Marijuana became law, and forced them to push new products. This latest move is last straw.

Miami - once America's cocaine capital; but no more. The War on Drugs has hit home. Today dealers and users play cat and mouse with the cops and live in dread of the Feds. And a new look drug scene has gone underground.

In Kensington north Philadelphia, heroin, crack cocaine and PCP are dealt from a hundred different corners. Kensington is a giant drug drive thru. But for the addicts and dealers it's a deadly trap that threatens to drive them literally insane.

Since the days of Kurt Cobain and grunge music, Seattle has been nicknamed Junkietown. The city's liberal laws and high demand for drugs is attracting gangsters and dealers looking to get rich. From the competitive crack business in Belltown to fashionable Molly users on the electronic dance music scene, National Geographic explores the highs and lows of Seattle's drug business.

Phoenix, Ariz., is the wholesale drug capital of America, under the control of one of Mexico's most powerful and ruthless drug organizations -Â- the Sinaloa Cartel. Almost 200 miles north of the Mexican border, the city has become the major stopping off point for the large-scale distribution and transshipment of marijuana, heroin and methamphetamine up from Mexico and out to the rest of the country.

Music and drugs go hand in hand in Nashville. For musicians who don't make it, drugs are the easiest way to make a living. National Geographic talks to a user and freelance cook who makes methamphetamine at home to cover his costs and get high. Then, learn how the 19th Judicial District Drug Task Force is faced with cleaning up after meth cooks' Â- operations that are both extremely dangerous and prohibitively expensive.

See the underground world of drugs through the eyes of its makers. A former British gangster serves as guide into this illicit underworld, visiting a secret hash-making location nestled in the mountains. Check out growers in Holland who are leading a horticultural revolution in high-grade cannabis. Follow a batch of raw opium from an Afghan poppy field to an Iranian heroin lab. Follow the supply chain of cocaine through the eyes of Colombian peasant farmers producing the drug in a paste.

The sale of drugs accounts for billions of dollars in illegal commerce across the globe, bringing untold wealth to a select few. But these men and women who live lavish lifestyles off the sale of drugs rarely associate themselves with the ugly underbelly where their products hit the streets — with users. These stories show that wherever people use — be it an island paradise or a cold city street — they can get lost in the shuffle. This episode will go deep into the stories of the users.