I am interested in protein tau. Tau is an intrinsically disordered protein, highly soluble in solution. In Alzheimer’s disease and other tauopathies, however, tau is found aggregated into tangles in the brain. In an effect to understand the underlying molecular mechanism, we have discovered that tau can be reversibly stored in high concentration by RNA through liquid-liquid phase separation (Zhang, X.(2017) RNA stores tau reversibly in complex coacervates. PLOS Biology ). It is not until recent years that liquid liquid phase separation has been found to be one of the major principles for cellular organization. Our current hypothesis is that tau biomolecular condensate formed through phase separation is directly involved in the tau physiological function and the relevant tau pathology.