Marijuana is a green, brown, or gray mixture of dried, shredded leaves, stems, seeds, and flowers of the hemp plant. You may hear marijuana called by street names such as pot, herb, weed, grass, boom, Mary Jane, gangster, or chronic. There are more than 200 slang terms for marijuana. Sinsemilla, hashish, and hash oil are stronger forms of marijuana. All forms of marijuana are mind-altering. In other words, they change how the brain works. They all contain THC (delta-9-tetrahydrocannabinol), the main active chemical in marijuana. They also contain more than 400 other chemicals. Marijuana's effects on the user depend on the strength or potency of the THC it contains. THC potency of marijuana has increased since the 1970s but has been about the same since the mid-1980s.Ways Marijuana is used.Marijuana is usually smoked as a cigarette (called a joint or a nail) or in a pipe or a bong. Recently, it has appeared in cigars called blunts.Amount of time Marijuana stays inside a person's body.THC in marijuana is strongly absorbed by fatty tissues in various organs. Generally, traces (metabolites) of THC can be detected by standard urine testing methods several days after a smoking session. However, in heavy chronic users, traces can sometimes be detected for weeks after they have stopped using marijuana.Marijuana among teens.Contrary to popular belief most teenagers have not used marijuana and never will. Among students surveyed in a yearly national survey, only about one in five 10th graders report they are current marijuana users. Fewer than one in four high school seniors is a current marijuana user.Why young people use Marijuana.There are many reasons why some children and young teens start smoking marijuana. Most young people smoke marijuana because their friends or brothers and sisters use marijuana and pressure them to try it. Some young people use it because they see older people in the family using it. Others may think it's cool to use...