RecruitingDevelopment of a Wearable Point of Care Monitoring Device for Pediatric Obstructive Sleep ApneaBackground: Obstructive sleep apnea (OSA) occurs when the blockage of the airway causes a person to stop breathing involuntarily for 10 seconds or more throughout the night during sleep. Pediatric OSA can be especially concerning and can have long-term effects. Researchers want to see how a monitoring device called near-infrared spectroscopy (NIRS) compares with the traditional techniques used in children s sleep studies. Objective: To learn about oxygen levels in the brain and limbs in children with and without sleep apnea using a wearable, point-of-care biosensor. Eligibility: Children aged 3-12 who have OSA and plan to receive treatment (OSA group) or who do not have OSA (NORM group). Design: Participants will be screened with a review of their medical records. If they have taken part in other NIH studies, that data will be reviewed as well. Participants in the NORM group will have 1 overnight study visit. Those in the OSA group will have 2 overnight study visits. Participants will do an overnight sleep study. They will have a physical exam and medical history. They will have a sleep study electroencephalography (EEG). For this, electrodes will be placed on their head. They will wear a gauze cap to keep the electrodes in place. Two NIRS probes made of a soft silicon will be placed on their forehead and arm. They will follow their normal bedtime routine. Their parent will stay overnight. The OSA group will have a second study visit 2 weeks to 12 months after they start treatment for their sleep apnea. They will repeat the sleep study.