INCLUSION CRITERIA:  In order to be eligible to participate in this study, an individual must meet all of the following criteria:  Male or female, aged 3 to 8 years For NORM group: Children without OSA (AHI<1) For OSA group: Children with OSA (AHI>=5)  EXCLUSION CRITERIA:  An individual who meets any of the following criteria will be excluded from participation in this study:  Children <3 years or >8 years Any chronic or acute medical condition severe enough to interfere with overnight sleep study acquisition. Taking any medications that are known to change sleep parameters within 2 weeks of screening polysomnogram. Any head injuries or physical conditions that in the opinion of the investigators would affect probe signal and contact. For NORM group: Children with AHI>1 For OSA group: Children with AHI<5