Volunteers are needed for an observational MRI study. We are using a new imaging technique to measure muscle metabolism in individuals with mitochondrial diseases and healthy individuals. To be potentially eligible for the study as a healthy volunteer, we require the following: -Healthy male or female -Between ages 7 to 25, inclusive -Not pregnant -Able to complete a 90-minute MRI scan Volunteers will meet with the principal investigator, Dr. Shana McCormack, MD, and complete a 1-day study visit at CHOP, including blood testing, questionnaires, and an MRI scan. Participants have the potential to earn study compensation. To learn more about the study and determine your eligibility, contact Sara Nguyen at email@example.com or (267) 426-7165.