Marijuana or cannabis is a soft drug that has been used by humans for thousand of years. It is endemic to south and central Asia and evidence of its use by Aryans, Assyrians, and Hindus of Asia are aplenty. The UN estimates that around 4% of world population use cannabis annually. In short, it is the number one used illegal drug in the world. Marijuana is produced from a plant called Cannabis Sativa or cannabis Indica. This plant also goes by the name Indian hemp. Marijuana is the name given to those parts of this plant which is smoked. The most important chemical agent in marijuana is a compound called tetrahydrocannabinol. However, marijuana smoke contains over 400 different chemicals including 66 other related cannabinoids. The debate on the use of medical marijuana in the United States and some other parts of the world has long been ended. In fact, marijuana now can be bought legally within 23 states of the US and other public stores in other parts of the world. There are now other countries such as Australia that are debating on the legalization of marijuana use.