Nicotine is a colorless, odorless substance that comes from the leaves of the tobacco plant. This liquid alkaloid is composed of carbon, oxygen, hydrogen and nitrogen.
For centuries, people were chewing and smoking tobacco leafs in the pursuit of sensations created by nicotine intake. When nicotine is highly concentrated, it behaves like poison and is used in insecticides to deter insects and animals. The reason that nicotine is so addictive is partly because of all of those pleasurable feelings it gives us. Additionally, adrenaline is released by nicotine when it is introduced to the body, which creates alertness in the mind. Secretion of endorphins , known as body`s natural pain-killers , is also increased by nicotine.
