Nicotine is an organic compound, an alkaloid found naturally throughout the tobacco plant, with a high concentration in the leaves. It constitutes 0.3 to 5% of the plant by dry weight, with biosynthesis taking place in the roots, and accumulates in the leaves.

It is a potent nerve poison and is included in many insecticides. In lower concentrations, the substance is a stimulant and is one of the main factors leading to the pleasure and habit   forming qualities of tobacco smoking.    Formal Chemical Name (IUPAC) (S)–3–(1-Methylpyrrolidin-2-yl) pyridine

                    
Nicotine has limited carcinogenic effects, inhibiting the body’s ability to destroy potentially cancerous cells; however, nicotine does not promote the development of cancer in healthy cells. In addition to the tobacco plant, nicotine is also found in lower quantities in other members of the Solanaceae (nightshade) family which includes tomato, potato, eggplant, aubergine), and green pepper. Nicotine alkaloids are also found in the leaves of the coca plant.