This project is the first involving the two most common neurodevelopmental disorders, ASD and ADHD, as well as TDC to establish a multi-dimensional database (clinic, behavior, neurocognitive function, brain imaging, metabolomics, and microbiome) using the same methodology. Based on this integrated multi-dimensional databank, we anticipate exploring metabolic flows of the gut-brain axis during brain development and identifying the common and unique biomarkers of ASD and ADHD and high-risk materials related to their functions and the underlying mechanism. Moreover, distinguishing the characteristics of the gut microbiota, gastrointestinal disorders, and microbial flora dysbiosis also helps us, in turn, to accelerate the process of identifying biological treatments that can interfere or slow down the severity of cognitive impairments in neurodevelopmental disorders. Eventually, we anticipate finding the clinical and neurocognitive measures related to the direct or indirect influence of gut-brain signaling. Our findings are anticipated to improve the knowledge about neurodevelopmental disorders, enhance developing early detection, diagnosis, and treatment for ASD and ADHD, and contribute to precision medicine.