"Nicotine is an alkaloid found in the nightshade family of plants (Solanaceae) that constitutes approximately 
0.6–3.0% of the dry weight of tobacco,[1][2] with biosynthesis taking place in the roots and accumulation occurring in the leaves. It functions as an antiherbivore chemical with particular specificity to insects; therefore nicotine was widely used as an insecticide in the past,[3][4] and currently nicotine analogs such as imidacloprid continue to be widely used."