The Children’s Hospital of Philadelphia is seeking healthy adolescents between the ages of 12-13, who are currently in the 7th grade, to participate in the Sleep and Growth Study 2. The purpose of this research is to learn more about the changes in sleep and body size in adolescents as they transition from middle to high school. Participants will be asked to visit CHOP so that we can measure their bone density. Following this visit, participants will wear a sleep tracker over a 2-week period and speak to a team member by phone on three occasions about the types of food eaten in the previous 24 hours. If you and your child agree to participate, the study will involve 3 visits over approximately 2 years. All participants are compensated for their time and effort. For more information and study details, please call 215-590-2383, ext. 1, or email s_grow@chop.edu.