Inclusion Criteria:  Case group, Sibling group and Control group:  Children aged under 18 years old; and The parents or legal guardian agree to hand in the stool samples of children; and agree to complete questionnaires; and The parents or legal guardian agree to sign the informed consent form for the children  Parent group:  Their suspected or confirmed ASD or ADHD children participated in the study; and Agree to hand in stool samples and complete questionnaires; and Agree to sign the informed consent consent  Exclusion Criteria:  All groups:  • Any subject taken probiotics, prebiotics, antibiotics 30 days before enrollment.  Subjects can be re-approached or join the study 30 days after taking probiotics, prebiotics, antibiotics.