Short abstract. High-resolution light microscopy (HR-LM) and X-ray diffractometry (XRD) were used in a non-destructive way to study the bulk structure of the Traditional Balsamic Vinegar of Modena (TBVM), an Italian specialty produced from cooked grape must and through a long aging process at room temperature. Data showed that TBV is a viscous food dispersion that may undergo solidification through both crystallization of the !-d-glucose and out-of-equilibrium phase changes. Due natural ability to self-associate into amorphous colloids and larger aggregates, a key role of polymeric melanoidins was also supposed into the development of vinegar bulk structure.