Cigarettes, Nicotine and Tobacco

C10H14N2

Tobacco, in its many forms, is the most used drug in the world. It comes in many different forms; cigarettes, cigars, chewing tobacco, snuff, and many others, however no matter how it is used, it's still always just as harmful.
Tobacco contains a substance called "nicotine", or if you want to get all scientific, C10H14N2. Nicotine is an addictive substance, which works as a sedative and a stimulant. It is very highly addictive and can cause an addiction from only one use. Initially, nicotine causes a very rapid release of adrenaline; you're probably aware of what this feels like. If you've worked on a very important project last minute, or been on an extreme thrill ride, you've felt it before; rapid heartbeat, increased blood pressure, quick and shallow breathing. Occasionally, adrenaline coupled with stress can have some useful effects such as hyper-awareness and significantly decreased reaction times. Nicotine usually just produces the first three effects. And in a bad way.
You've probably heard that smoking a cigarette can make you feel happier, or better, and that's why some people smoke a lot. That's partly true. Nicotine causes the brain to release an excess amount of endorphins, a chemical that causes you to feel "happy". There also are other substances that cause that too, like chocolate, so this isn't unique to nicotine. What happens when people smoke a lot of nicotine, is that the brain becomes "accustomed" to this abnormal amount of endorphins, and so can cause depression when the smoker doesn't have a cigarette in their mouth. That causes the smoker to pull out another, and so begins a cycle of even more addiction.

When you smoke, however, it's not just the nicotine that affects you. Laced in that smoke are other dangerous chemicals such as cyanide, formaldehyde, carbon monoxide, and perhaps dozens of others which are even more deadly. All of these chemicals are either poisonous or can cause cancer, and that's what happens to most smokers.

And if that's not enough to convince one to not smoke; here's another fact.
When all the nicotine is stored, in all they warehouses and all, some rodents and insects accidentally eat some of the tobacco, and die right there in the tobacco. What do the manufacturers do with them before they make the cigarettes? Nothing.

Drugs?

Everybody's heard of drugs, right? If you don't, a drug is defined as a substance that causes a physiological effect on a person when ingested or otherwise introduced to the body.  Many people may tell you that there are two kinds of drugs, the good and the bad kinds. However, all drugs can have good or bad effects depending on how they're used. Some are medical prescription drugs you've probably never heard of, such as methylphenidate, or β cell inhibitors. There are also OTC or over-the-counter drugs, which you might have heard of, such as ibuprofen, aspirin, or acetomenaphine. And then there are those that everyone knows about, or the "bad" drugs such as methamphetamine (meth), cannabis (marijuana), and the ever present alcohol, tobacco, and nicotine.