Nicotine. Molecular graphic of nicotine, an addictive alkaloid drug found in tobacco. The molecule is represented here as cigarettes. Nicotine (formula: C10.H14.N2) is an oily, colourless liquid. Atoms are colour-coded: carbon (white), nitrogen (glowing ash) and hydrogen (orange filters"). Nicotine is the active component of tobacco. In small doses, it stimulates the autonomic nervous system, but tolerance builds up fast, leading to addiction. As well as the toxic effects of nicotine, smoking tobacco can lead to serious lung problems, including lung cancer."