At present, many teenagers smoke. I don't think it's a good phenomenon. It must be stopped, for smoking is harmful in many ways.
First, smoking is bad for our health. As we start smoking, it's so difficult to give up, because the tobacco contains a drug called nicotine, which can get us into the habit of smoking. When we go without nicotine, our bodies will feel sick.
Second, smoking is so dangerous. When we smoke in bed, we may kill ourselves as well as burn down our houses, for burning cigarette ends may cause a big fire. And if we threw the cigarette ends anywhere, it would also cause a fire disaster.
Furthermore, once we smoke in public, we may make other people feel uncomfortable as well.
Accordingly, for the sake of your and others' health, please don't smoke.