Why Young Adults Should Not Smoke E-cigs/cigarettes

How would we discourage young adults from smoking? It is their body and they can do what they want. Just don’t how to convince them to have a better and healthier lifestyle. Same thing with e-cigs. We honestly have no idea what is in those “juices” but people use it to get away from smoking, but I feel as if people now do it just do it to fit in the crowd.