Metabolomics is one of the newest “omics” sciences that is being applied to date to investigate several aspects of pathologies and medical topics in general. It provides a snapshot of the metabolic state of an individual by the detection of metabolites in several biological fluids, such as saliva, blood and sweat. Our research group has more than a decade of experience in this field and we ourselves applied this technology to investigate, for instance, every aspect of breast milk, different neonatal diseases and neuropsychiatric disorders. In this paper, which is adapted from the lecture given by Professor Fanos at the 5th edition of the Galatia Congress (2021), we discuss the usefulness of metabolomics in the investigation of paediatric neuropsychiatric disorders. We are convinced that this technique, in the future, will provide all the answer to the infinite questions concerning the paediatric brain and its disorders, in order to help the clinicians and families of these children to give the best life possible to these little patients.</em