In this article, we present the main methodological principles of symptom networks in psychopathology. It is a topological approach linking entities from different scales of analysis of an individual (from genetics to behavior, via cerebral connectivity). They are an alternative to the Diagnostic and Statistical Manual of Mental Disorders (DSM) and Research Domain Criteria (RDoC), but they do not exclude them. Symptom networks exceed or circumvent some limits of these classifications. Furthermore, they contribute to the stratification and organization of these nosologies. Behind the originality of its methodology, this program proposes a redefinition of mental illness which modifies the conception of psychiatry. But their future is still uncertain: they must take on an epistemological and methodological challenge. At the same time, they have to convince the community of mental health researchers and clinicians of their utility and value.