The value of exercise studies in children often resides in defining differences, which might make growing youngsters unique from their mature adult counterparts. Many such physiological and behavioral developmental differences have been identified, emphasizing that children are not, physiologically speaking, simply small adults. The following 2 studies published in the past year were chosen for their importance in contributing to the insights into previously unexplored areas. The first study addresses the influence of exercise on physiological variability, an emerging field that offers to provide important insights into the nature of such responses. The second study concerns the effects of altitude on physiological responses to exercise, an area of considerable importance for the health and physical performance of pediatric athletes, climbers, and residents at high altitude. These studies exemplify the genre of investigations that are essential for advancing our understanding of the link between exercise with physical performance and the well-being of growing children and adolescents.