Autism Spectrum Disorder (ASD) is the most prevalent of the developmental disorders and their incidence is rising. However, the variability in the behavioral symptoms is large. In part for these reasons, the ASD clinical diagnosis is challenging and often is not made until 3-5 years of age. Thus, there remains an unmet need for a valid and reliable marker which would facilitate ASD diagnosis early in life, enable efficient study of ASD risk factors, and eventually serve as a useful marker to inform the development of effective therapies and assess treatment response in future clinical trials. The specific brain based marker that investigators are currently evaluating is brain plasticity (the changes that occur in your brain through experience). Investigators measure brain plasticity using noninvasive brain stimulation including transcranial magnetic stimulation (TMS) combined with brain imaging, EEG, and behavioral outcome measures. Their work to date demonstrates the potential utility of these techniques in higher-functioning adolescents and adults with ASD, and pilot data support the feasibility and safety of applying the same measures to children and lower functioning individuals.