Tobacco is made from the dried leaves of the tobacco plant. When ingested, tobacco has a stimulant effect (i.e., it speeds up the messages travelling between the brain and body). One of the chemicals which naturally occurs in tobacco is nicotine. Nicotine is toxic and highly addictive. The cultivation and production processes involved in making tobacco products also introduce many other chemicals. These include pesticides, herbicides and fertilisers, as well as hundreds of chemical additives to increase flavour and addictiveness.