For many years, clinical trials were conducted only in adults. To treat children, a common approach has been to use data from adults and adjust the dose of the medication according to a child’s weight. But children are not simply small adults. Many factors affect the way they respond to treatments, including the growth and maturation of their organs, changes in metabolism throughout infancy and childhood, and changes in body proportion. In recent years, through a combination of new legislation and incentives for manufacturers, the number of pediatric clinical trials has increased. The FDA applies strict guidelines to children’s participation in these studies.