Opiates start with the opium poppy. The substances made from that plant, such as heroin and codeine, affect our pain and pleasure centers of the brain. Since the 1930s, heroin has captured more headlines than any other opiate. There are approximately five to ten million heroin abusers worldwide. Since the 1940s, Mexico has been the major supplier of heroin to the United States. In the 1980s, a new form of Mexican heroin, known as “tar” or “black tar,” has taken over most of the market. There are major increases in the production of heroin in Southwest Asia, which can be more than 90 percent pure. At the present time, injection is the preferred means of abusing heroin in the West. Heroin as an opioid usually will develop tolerance and tissue dependence. Since tolerance occurs rather rapidly with opioids users might need ten times their initial dose within a month of beginning use.