The present study gives a new understanding about bitumen＇s colloidal behavior, related to its chemical composition, microscopic structure and rheological properties. Bitumens possess a strong temperature dependence of rheological properties, governed by the interaction of the individual constituents. Much importance is given to the colloidal index of the bitumen, based on the ratio of the four main chemical components (asphaltenes, resins, aromatics, saturates). Increasing one of these constituents fundamentally changes the structure and the theological behavior of bitumen. Therefore, a gel bitumen contains high asphaltene/resin concentrations, leading to a network structure with high rigidity and elasticity (high IG*I, low delta), whereas a sol bitumen possesses a high resin/asphaltene ratio, forming domains of coherent asphaltene micelles which lead to a good time-temperature equivalence in the Black space but also high viscous behavior.