Marijuana, also known as cannabis, is an annual plant that is grown worldwide for its fibers, which are used to make hemp fabric, its seeds, which are used for birdseed, and its buds, which can be smoked for recreational and/or medicinal purposes. Marijuana plants are usually between 1 and 5 feet tall and can thrive in a variety of climates given adequate light, including indoor "grow rooms."

The plant is thought to have originated in Central Asia, near present-day Tibet. Evidence of marijuana's use and cultivation stretches back to 10,000 BC, represented by charred marijuana seeds found in a ritual brazier in Romania. It is estimated that about 4% of the world's adults use marijuana annually and 0.6% use it daily. This translates to about 264 and 40 million people respectively.

Much of marijuana's fame -- and controversy -- comes from its use as a psychoactive drug. As a drug, marijuana has many names -- ganga, weed, trees, etc. In many countries, marijuana is expensive (~$20 US Dollars (USD) a gram) because its use as a drug is either illegal or tightly regulated. In many other countries, however, like Mexico, Canada, the Netherlands, Spain, Australia, Russia, Iran, France, and Italy, marijuana is either legal or nominally illegal but the penalties for its use are rarely enforced in practice. This makes the plant less expensive and more widely available.

When smoked, marijuana gives the user a "high," a mild feeling of elation, pleasure, and wonder. The onset is rapid, about 2-5 minutes, and lasts for about 30 minutes to three or four hours, depending on the dose. Being high on marijuana changes the way people interpret sounds and color, making auditory and visual experiences more stimulating and intense. This is why marijuana use was been intensely promoted by music fans in the 60s and 70s, and marijuana continues to be used frequently at rock concerts. Marijuana gives the user a soothing sensation which diminishes the pain of diseases like cancer and AIDS.

Besides the positive aspect, marijuana has some downsides. It may cause a slight feeling of paranoia in the user, which may exacerbate pre-existing paranoia derived from using an illegal drug in the first place. Marijuana causes lethargy and poor motor coordination, meaning that operating heavy machinery or driving under the influence is inadvisable. In some countries, marijuana is illegal, meaning that being caught with it can lead to fines or jail time. In some countries and areas, like Hong Kong for instance, marijuana is so illegal that growing or distributing it can lead to life imprisonment.