Objective: The main objective of this proposal is to develop a minimally-invasive biological assay that can be widely used to identify variations in mitochondrial function and dysfunction in children with autism spectrum disorder (ASD). This assay will allow the investigators to determine the true range of mitochondrial function and dysfunction across a population of children with ASD. The relationship between mitochondrial function and dysfunction in ASD, redox metabolism and core ASD symptomology will also be investigated. To understand the true variation in mitochondrial function and its relationship to cognitive development and autism symptoms, participants will be evaluated at two time points to understand the within subject variation of mitochondrial measurements.