About one in four youths used a tobacco product during the past 30 days. By school level, this is approximately three in ten high school students and one in eight middle school students. Since 2014, e-cigarettes have been the most commonly used tobacco product among youths. It is reasonable to assume that many young smokers are practicing this habit while with friends or at parties, exposing their friends and peers to hazardous passive smoking, which is also the case for smaller children exposed to their parental smoking. Smoking is just one important public health issue in childhood and adolescence, but there are many other issues in this period of our development. In this book we have gathered some recent research on children and youth from various places around the world on many topics, not just limited to smoking, which we hope will be of interest to the reader.