U.S. government researchers launched the biggest-ever study of children on Tuesday, saying they will track 100,000 children from birth through age 21 to see what makes kids sick. The study, being launched at 96 centers, will follow the children as they grow up, looking at their environments, behavior, family and genetics. “Together the children from these 96 locations will represent the face of all of America’s children,” the National Institute of Child Health and Human Development, which is sponsoring the study, said in a statement. The National Institutes of Health, the Centers for Disease Control and Prevention and the Environmental Protection Agency will work together on the study, detailed on the Internet at http:/nationalchildrensstudy.gov/about/mission/overview.aspx.